Although playing video games is one of the most popular leisure activities in the world, research into its effects on players, both positive and negative, is often trivialised. Some of this research deserves to be taken seriously, not least because video game playing has implications for health.1 One innovative application of video games in health care is their use in pain management. The degree of attention needed to play such a game can distract the player from the sensation of pain, a strategy that has been reported and evaluated among paediatric patients. One case study reported the use of a handheld video game to stop an 8 year old boy picking at his face. The child had neurodermatitis and scarring due to continual picking at his upper lip. Previous treatments had failed so the boy was given a hand held video game to keep his hands occupied. After two weeks the affected area had healed. Controlled studies using both randomised controlled trials and comparison with patient's own baseline measures show that video games can provide cognitive distraction for children during chemotherapy for cancer and treatment for sickle cell disease.2-5 All these studies reported that distracted patients had less nausea and lower systolic blood pressure than controls (who were simply asked to rest) after treatment and needed fewer analgesics. Video games have been used as a form of physiotherapy or occupational therapy in many different groups of people. Such games focus attention away from potential discomfort and, unlike more traditional therapeutic activities, they do not rely on passive movements and sometimes painful manipulation of the limbs. Video games have been used as a form of physiotherapy for arm injuries,w1 in training the movements of a 13 year old child with Erb's palsy,w2 and as a form of occupational therapy to increase hand strength.w3 Therapeutic benefits have also been reported for a variety of adult populations including wheelchair users with spinal cord injuries,6 people with severe burns,7 and people with muscular dystrophy.w4 Video games have also been used in comprehensive programmes to help develop social and spatial ability skills in children and adolescents with severe learning disability or other developmental problems, including autismw5 w6; children with multiple handicaps (for example severely limited acquisition of speech)w7 w8; and children with impulsive and attention deficit disorders.w9 However, there has been no long term follow-up and no robust randomised controlled trials of such interventions. Whether patients eventually tire of such games is also unclear. Furthermore, it is not known whether any distracting effect depends simply on concentrating on an interactive task or whether the content of games is also an important factor as there have been no controlled trials comparing video games with other distractors. Further research should examine factors within games such as novelty, users' preferences, and relative levels of challenge and should compare video games with other potentially distracting activities. While playing video games has some benefits in certain clinical settings, a growing body of evidence highlighting the more negative aspects of play—particularly on children and adolescents. These include the risk of video game addiction,8,9 (although the prevalence of true addiction, rather than excessive use, is very low8) and increased aggressiveness.10 There have been numerous case reports of other adverse medical and psychosocial effects. For instance, the risk of epileptic seizures while playing video games in photosensitive individuals with epilepsy is well established.11,12 w10 w11 w12 Graf et al report that seizures are most likely to occur during rapid scene changes and when games include patterns of highly intense repetition and flickering.12 Seizures and excessive or addictive play do not seem to be linked directly, however, as occasional players seem to be just as susceptible. Other case studies have reported adverse effects of playing video games, including auditory hallucinations,w13 enuresis,w14 encopresis,w15 wrist pain,w16 neck pain,w17 elbow pain,w18 tenosynovitis,w19-w22 hand-arm vibration syndrome,w23 repetitive strain injuries,w24 peripheral neuropathy,w25 and obesity.w26-w28 Some of these adverse effects seem to be rare and many resolve when the patients no longer play the games. Furthermore, case reports and case series cannot provide firm evidence of cause and effect or rule out other confounding factors. On balance, given that video game playing is highly prevalent among children and adolescents in industrialised countries, there is little evidence that moderate frequency of play has serious acute adverse effects from moderate play. Adverse effects, when they occur, tend to be relatively minor and temporary, resolving spontaneously with decreased frequency of play. More evidence is needed on excessive play and on defining what constitutes excess in the first place. There should also be long term studies of the course of video game addiction.