The difficulties of performing prospective psychiatric follow-up studies have recently increased due to growing concern over the ethical issues involved. In a study to determine the efficacy of different lengths of psychiatric hospitalization 235 patients were followed for 2 years after study hospitalization. Data were obtained on more than 90 per cent of the patients. The cost of performing 100 follow-up interviews ranged from $9,169 for patients living within a 6-mile radius of the study site, to $17,942 for patients living within the contiguous United States. It is concluded that through persistent effort useful data can be obtained by follow-up of psychiatric patients, while maintaining ethical standards which include respect for the rights and wishes of the patient.