The aim of the present study is to report actual information about the clinical conditions of psychiatric inpatients in 31 psychiatric hospitals all over the country. The schedule used in this survey was partly designed following the information gathered in the NKI Mental Health Information System, including other relevant variables to facilitate operational and evaluative research. The survey was carried out by the health personnel of each unit, following the instructions included in a brief manual. All the inpatients from the psychiatric hospitals with 150 beds or less were included. For those units with more capacity, a systematic random sample, including one of every five patients was used. The final sample contained 4 539 inpatients. Sixty percent corresponded to male inpatients, most of them single, with schizophrenia and alcohol and drug dependence as the most frequent diagnoses. In women, the most frequent diagnoses were mental retardation and other chronic organic psychosis. As a whole, 59 % of the patients were reported with a chronic illness. Among the actual clinical problems, psychotic states were the more frequently reported. Disabilities were reported in 65 % of the sample; 51 % presented a second one and 37 % three. Those having a severe disability were more predominat in the extreme aged groups. Thirty six percent of the patients had been abandoned or rejected by their families or did not have any relatives. Females were predominant in this situation, associated with the more severe and incapacitating disorders. Half of the population had the possibility of being discharged; the 40 % of patients without this possibility included those with mental retardation and epilepsy. The findings of the present report are disscussed and compared with previous somehow similar studies in Mexico. As the information gathered in the study is quite extensive, further reports will present data on acute and chronic patients, specific disorders, hospitalization length, readmissions, specific disabilities and other related variables.