The classification of mental disorders is a quite important albeit complex issue; a universal classification system is essential to making comparisons among international mental health statistics. As far back as 1961, Kramer demonstrated that the difference in the admission rates for affective psychosis was surprisingly large between American and British mental hospitals, and subsequently, a crossnational study between the UK and the US (Cooper, J.E. et al., 1969), was carried out to clarify the cause of this discrepancy. Another international study carried out for the diagnosis and classification of mental disorders, was named the ?gInternational Pilot Study of Schizophrenia?h (WHO, 1979). These efforts gave rise to a more basic question in mental health statistics: ?gAre discrepancies found among countries' admission rates due to real differences in patients' clinical states, or are they due rather to differences in the diagnostic criteria? In an attempt to address this controversy (Jablensky, A., 1988), two computer classification systems featuring objective criteria have been developed, each claiming to increase the comparability; DSM III in the US (A.P.A., 1980; Robins et al., 1981) and CATEGO in the UK (Wing et al., 1974). DMS III is a diagnostic criteria which includes the computer program ?gDIAGNO?h; CATEGO is a computer program based on the ninth edition of International Calssification of Diseases (Cooper, J.E., 1988). Here arises another problem: Are these computer classifications really compatible (Watkins, S., 1988)? The current study is limited to depression. As depression is currently involved in several disputes about the overall nature and classification of mental illneses (Kendell, R.E., 1976).