Eighty patients on an acute intensive treatment ward of a Veterans Administration neuropsychiatric hospital were divided into 4 groups matched for age, diagnosis and number of months of previous psychiatric hospitalization. Each of 2 trained activity therapists took one of these groups daily for a half day in a traditional occupationaltherapy type of situation and one group daily for a half day on a lawn-mowing detail using hand mowers on the hospital lawn. After 12 weeks the degree of improvement shown by each patient was rated by the ward psychiatrist who did not know the assignments of the particular patient.The results indicate that the nature of the therapeutic activities differed, and that these important differences, plus the wide differences in the personalities of the therapists, greatly affect patient improvement and readiness for discharge. Patients mowing the lawn showed significantly more improvement than patients working in O.T. (P=.004). It would appear that for the type of psychotic patient included in this study, the simple, co-operative and useful activity of mowing the lawn is more beneficial than the less vigorous, more potentially creative, more complex, but possibly more isolated activity of individual occupational therapy projects.