There is inadequate data about the association between specific psychosocial factors and pediatric health care use. We hypothesized that maternal substance abuse, depression, and low social support would be associated with increased medical visits, emergency room (ER) use, visits for injuries and delays in immunization. We conducted a prospective study of 202 U.S. families with preschool children in a clinic serving the inner city poor. Psychosocial factors were assessed from standardized screening questionnaires for substance abuse, depression and low social support. Research assistants blind to the study hypothesis reviewed medical records for health care over the year following completion of the questionnaire: number of clinic visits, use of emergency room, visits to the ER or clinic for injuries, and delays in immunizations of two months or more. Among the 202 mothers, the mean age was 24.4 years, 47% were African American, 32% Caucasian, and 14% Asian; 55% were high school graduates. The average household income was $7620 per year; the mean age of children was 12.2 months. Thirty-seven percent of mothers screened positively for substance abuse, 34% for depression, and 60% for low social support. Children had an average of 8.6 clinic visits per year; 41% had an ER visit, 21% had an injury resulting in an ER or clinic visit, and 43% of children under 2 years of age had a delay of 2 months or more in recommended immunizations. After controlling for maternal and child age in a regression equation, none of the psychosocial factors were significant predictors of health care use outcomes.(ABSTRACT TRUNCATED AT 250 WORDS)