Androgens may play a role in the hyperkeratinization of acne follicles. The goal of our study is to test the hypothesis that infrainfundibulular keratinocytes of acne subjects produce more androgens than those from normal subjects. Thus, the specific activities of 5α-R and 17β-HSD, which are responsible for the production of testosterone (T) and dihydrotestosterone (DHT), were determined in follicular and epidermal keratinocytes.Skin biopsies were obtained from the foreheads of 32 men and women both wit and without acne. Keratinocytes were cultured from epidermis and infrainfundibular segments of pilosebaceous follicles. Steroid metabolism studies with radiolabeled T and androstenedione were performed in keratinocyte homogenates to determine the activity of 5α-R and the oxidative and reductive activities of 17β-HSD. Prior to the biopsies, acne lesion counts were performed and casual sebum output was measured using Sebutape R . Serum levels of T, androstenedione, DHT, DHEAS and 3α-androstanediol glucuronide were determined using radioimmunoassay. In all samples tested, activities of 5α-R and 17β-HSD were higher in keratinocytes from the infrainfundibulum compared to those from the epidermis. Mean activities (± SEM) of 5α-R were higher in infrainfundibular keratinocytes from acne females (1.52 ± 0.33 pmol/min/mg protein, n=5) vs. nonacne females (1.21 ± 0.31 pmol/min/mg protein, n=10) and acne males (2.35 ± 0.83 pmol/min/mg protein, n=6) vs. nonacne males (1.47 ± 0.3 pmol/min/mg protein, n=7). A similar relationship was noted for both the oxidative and reductive activities of 17β-HSD with higher activities noted in subjects with acne compared to those without acne. Data on serum androgen levels, sebum excretion rate and correlations with 5α-R and 17β-HSD activity in follicular and epidermal keratinocytes will be presented.