Environmental factors related to physical assault by patients were examined to identify clinical implications warranting further investigation and to test methodology. The concepts of ward conditions (degree of patients' illness, numbers of patients and staff) and ward climate were the focus of the study. Participants were patients and nursing staff on two acute and four long-term psychiatric units in a large neuropsychiatric hospital. Patients and staff were asked to complete the Ward Atmosphere Scale to assess ward mood and climate. Each assault incident was identified from the daily nursing ward report. With each assault occurrence, the nurse manager was asked to complete a questionnaire about environmental conditions at the time of the assault. Most assaults occurred during meal times and afternoons. The most frequent locations were ward corridors and dayrooms. There appeared to be an inverse relationship between assault frequency and number of staff. Crowding rather than total number of patients per ward was suggested as a factor related to assault. Degree of patient acuity seemed to be inversely related to assault frequency. There were suggested trends between assault frequency and a low score on autonomy and a high score on staff control. Clinical implications, ideas for further research, and improved design measures are suggested. The challenge to understand and control this complex phenomenon remains a critical issue for inpatient nursing care.