BACKGROUND: Evidence suggests the type of treatment received for prostate carcinoma is associated with comorbidity, but little information is available on associations with specific comorbid disease or symptoms. The authors examined the relations between treatment and comorbidity, specific comorbid disease, and symptoms. METHODS: Medical records were abstracted for 1054 male members of the Kaiser Permanente medical care program diagnosed with prostate carcinoma from 1975 to 1987. Information was obtained on demographic characteristics, comorbid conditions, symptoms, tumor stage and grade, and treatment. Logistic regression was used to determine the significant predictors of treatment (radiation vs. nonaggressive treatment and surgery vs. nonaggressive treatment). RESULTS: Compared to nonaggressive treatment, radiation treatment was less likely among men who had prior cancer (adjusted odds ratio [OR] 0.29, 95% confidence interval [CI] 0.09-0.90) or cerebrovascular disease (OR 0.33, 95% CI 0.13-0.83). There was a significant interaction between race and myocardial infarction (P = 0.02). Surgery, compared to nonaggressive treatment, was less common among men with a prior cancer (OR 0.21, 95% CI 0.07-0.63) or congestive heart failure (OR 0.29, 95% CI 0.09-0.90). Significant interactions were observed between race and myocardial infarction (P = 0.01), diabetes and dysuria or hematuria (P = 0.02), and para- or hemiplegia and urinary frequency or nocturia (P = 0.01). CONCLUSIONS: Specific symptoms and comorbidity appear to influence treatment for prostate carcinoma. More research is needed on treatment differences by race.