PURPOSE. This paper aims to provide insight into nursing classifications and to report the effects of nursing diagnostics implementation. This paper summarizes the results of six studies. METHODS. Two systematic reviews, instrument development and testing, a pre–post intervention study, and a cluster-randomized trial were performed. FINDINGS. The NANDA International classification met most of the literature-based classification criteria, and results showed the Quality of Nursing Diagnoses, Interventions and Outcomes (Q-DIO) to be a reliable instrument to measure the documented quality of nursing diagnoses, interventions, and outcomes. Implementation of standardized nursing language significantly improved the quality of documented nursing diagnoses, related interventions, and patient outcomes. As a follow-up measure, Guided Clinical Reasoning (GCR) was effective in supporting nurses’ clinical reasoning skills. CONCLUSIONS. Carefully implementing classifications led to enhanced, accurately stated nursing diagnoses, more effective nursing interventions, and better patient outcomes. IMPLICATIONS. Rethinking implementation methods for standardized language and using GCR is recommended. Based on the results of this study, the inclusion of NANDA International diagnoses with related interventions and outcomes in electronic health records is suggested. [ABSTRACT FROM AUTHOR]