Acquired immune deficiency syndrome (AIDS) became the leading cause of death among Maryland State prisoners in 1985. To identify the prevalence, risk factors, and temporal trends for infection with the human immunodeficiency virus type 1 (HIV-1) in the statewide prison system, excess sera were obtained from incoming male inmates during specified periods between April and June 1985, 1986, and 1987. Correctional medical personnel also provided demographic variables of age, race, offense category, sentence, jurisidiction, and an indicator of intravenous drug use. Once rendered anonymous, specimens were assayed for antibody to HIV-1, using ELISA and Western blot techniques. For data from April to June 1985, 1986, and 1987, the crude prevalence of anti-HIV-1 was 7.1, 7.7, and 7.0%, respectively. Although one-third of incoming inmates were identified as intravenous drug users (IVDUs), the drug use variable was missing for 70% of the 1985 sample, and 40% of the 1986 sample. Several strategies were used to examined temporal trends in the context of missing data. Univariate analyses suggested no substantial change over time for either HIV-1 seroprevalence or risk of infection among IVDUs.(ABSTRACT TRUNCATED AT 250 WORDS)