Neurocognitive impairment and social dysfunction has been reported in patients with bipolar disorder, and several studies have reported a relationship between neurocognition and social functioning in this group. Although some studies had suggested neurocognitive and social dysfunction in the early phases of bipolar disorder, there was little research on bipolar disorder patients diagnosed with a first manic episode at the planning of this thesis. The studies of social functioning in bipolar disorder had also been disadvantaged by the multitude of different assessment instruments in use. The first aim of study was therefore to establish reliability and validity of the Norwegian version of a well-known assessment instrument for social functioning – the Social Functioning Scale. The scale, originally developed for schizophrenia patients, was found to have good psychometric properties and was applicable for patients with bipolar disorder as well as for patients with schizophrenia. Although studies of neurocognition in the early phases of bipolar disorder were few, the existing literature had reported neurocognitive deficits in first-episode mania. Studies comparing neurocognitive functioning in first-episode patients to multiple-episode samples were few and inconclusive, and few studies had investigated to what degree first-episode patients showed clinically significant cognitive impairment. The second aim of the study was to describe neurocognitive functioning and the magnitude of dysfunction in a group of patients with first contact mania to an age, gender and education matched sample of healthy control participants. Patients were separated into two groups according to their number of previous manic episodes – one group consisting of patients with only one previous manic episode (First Manic episode; FM), and a second group with patients who had experienced multiple although untreated previous manic episodes (Previous manic episode; PM). Consistent with findings from two other studies of first episode mania patients we found statistically significant differences with moderate to large effect sizes between both patient groups and the healthy control group on measures of verbal recall, psychomotor speed, attention and some aspects of executive functioning as well as visuoconstructive reasoning. Psychomotor speed was the domain with the largest group differences. Eighteen percent of FM patients and sixteen percent of PM patients were considered clinically significantly impaired across cognitive measures. Comparing the present findings to a non-overlapping sample of multiple-episode bipolar disorder patients from our study group suggests comparable dysfunction in some aspects of verbal recall and executive functioning, and consistently smaller deficits among the first-episode group on the remaining neuropsychological measures. Studies of social functioning in patients who have recently been hospitalized for a first manic episode have found that about half of this group experience social dysfunction even after remission of clinical symptoms. When planning this thesis, there were no previous studies that had examined the relationship between neurocognition and social functioning in first episode mania. The third aim of the study was therefore to investigate both self-rated and clinician-rated social functioning in first-episode mania, and the relationship between social functioning and neurocognition. We found that compared to a matched healthy control sample, patients with first-episode mania displayed statistically significantly poorer selfrated social functioning on all subscales of the Social Functioning Scale. In addition, patients with previous untreated manic episodes rated themselves as being less competent in performing independent living skills, participated less in social activities, were less likely to be engaged in full-time employment and had a lower overall SFS score compared to patients with a first manic episode. There was also a relationship between a number of clinical measures and both self- and clinician-rated social functioning in the combined patient group. Depressive symptoms and processing speed had an independent contribution to self-rated social functioning, while psychotic symptoms significantly influenced clinician-rated social functioning. These findings suggest that neurocognitive dysfunction is present early in the course of bipolar disorder and reaches the level of clinical significance in a subgroup of individuals. Comparing our results with multiple-episode patients, the findings also suggest that the neurocognitive dysfunction may increase with illness progression. Results also show that impairment of social functioning in BD is present already after a first manic episode, and is associated with a number of clinical variables although depression had the largest influence on self-rated social functioning. Neurocognition, except from processing speed, did not appear to play a significant role in social functioning at this stage. Still, the findings underline the importance of assessing neurocognitive functioning in patients with bipolar disorder early in the illness course, and suggest that at least a subgroup of patients might benefit from treatment aimed at enhancing cognitive functioning. As depressive symptoms were strongly related to social functioning, complete functional recovery after a depressive episode should therefore be the goal of treatment as well.