Monthly serum dehydroepiandrosterone sulfate, androstenedione, testosterone, dihydrotestosterone, and free testosterone levels were measured in 94 of 129 patients with castration resistant prostatic carcinoma treated on a clinical protocol with aminoglutethimide (1000 mg/day) plus hydrocortisone (40 mg/day) Base-line steroid levels were not found to be age related. Therapy reduced the median levels of all monitored steroids but this suppression was not uniform. Although 87% of dehydroepiandrosterone sulfate levels were suppressed compared to base-line measurements, only 52% of androstenedione and 49% of testosterone levels were reduced. Androstenedione levels in 34% of patients actually rose to greater than twice base-line levels with similar but less frequent rises seen in testosterone, free testosterone, and dihydrotestosterone levels. The highest testosterone level measured was 190 ng/ml. Neither the cause, the deviation, nor the clinical significance of the androgen rise seen in these patients was established. Therapy with aminoglutethimide plus hydrocortisone as administered in this study may not uniformly achieve the objective of suppressing adrenal androgen production.