Hospitalization for mental disorders (Major Diagnostic Categories 19 and 20) was examined using the 1980 Hospital Discharge Survey (HDS) data. We added to the HDS data by noting whether each hospital had a specialized psychiatric and/or chemical dependency unit, especially noting short-term specialty psychiatric and chemical dependency hospitals. Of the approximately 1.7 million episodes with MDC-19 and -20 diagnoses in the nation's nonfederal short-term hospitals in 1980, 13.5 percent were in specialty hospitals. Of the remaining general hospital episodes: 31 percent occurred in hospitals with only psychiatric units, 5 percent in hospitals with only chemical dependency units, 31 percent in hospitals with both types of specialized treatment units, and 33 percent in hospitals with neither type of unit. The last figure is much less than previously thought. The five hospital types may be arrayed on a continuum of resource utilization and severity of cases treated, with general hospitals with no special units at one end, specialty hospitals at the other, and general hospitals with psychiatric or chemical dependency units intermediate. Presence or absence of a chemical dependency unit influences a hospital's profile in this regard, particularly for MDC-20. Future studies should take into account the presence of a chemical dependency unit.