Abstract Plasma concentrations of sex hormone binding globulin (SHBG), testosterone, free testosterone, androstenedione (A4) and levonorgestrel were studied in 17 women before and during use of two levonorgestrel covered rods resulting in identical plasma concentrations of levonorgestrel as Norplant® implants. There was a highly significant decrease in SHBG during treatment. Total testosterone and A4 also decreased significantly. Free testosterone remained unchanged. Diurnal variations were found to occur for A4, total and free testosterone, but not for SHBG or levonorgestrel. Moreover, plasma concentrations of testosterone, free testosterone, levonorgestrel and SHBG were measured in a second group of 88 women participating in a clinical study on Norplant® implants, who at the one year follow-up visit either denied or claimed to have developed increased facial acne during treatment. There was no difference regarding SHBG, total testosterone, free testosterone or levonorgestrel between the groups of women with and without facial acne. However, the women in the group noticing increased acne during treatment, reported significantly more often to have had acne before treatment compared to the women who did not notice increased acne during treatment. It is concluded that treatment with Norplant® implants does not result in increasing plasma levels of androgens.