The aim was to assess the efficacy and safety of a low-dose oral contraceptive containing norethindrone acetate (NA) and ethinyl estradiol (EE) (Estrostep; Parke-Davis Morris Plains New Jersey) compared with placebo in the treatment of moderate acne vulgaris and the impact of treatment on quality of life. A total of 593 women ranging in age from 14 to 49 years were enrolled in two identical randomized double-blind placebo-controlled parallel-group multi-center studies over six 28-day cycles. 297 subjects received NA/EE (1 mg NA/20 mcg EE for 5 days 1 mg NA/30 mcg EE for 7 days and 1 mg NA/35 mcg EE for 9 days) and 296 received placebo. Efficacy for primary end points was determined by changes in acne lesion counts and an investigators facial acne global assessment. In addition differences in mean scores of 4 domains of an acne-specific quality-of-life questionnaire (Acne-Qol) were examined. Estrostep-treated subjects showed a significantly greater decrease from baseline in lesion counts at study exit including inflammatory lesions (P = 0.0014) comedones (P = 0.0003) and total acne lesions (P < 0.0001) relative to placebo. A significantly greater proportion of Estrostep-treated subjects had investigator ratings on the FAGA of absent minimal or mild compared with placebo (P = 0.0004) at the end of the study. In addition Estrostep-treated subjects had significant improvements in Acne-QoL ratings versus placebo with improvements in all four domains: self perception role-emotional role-social and acne symptoms (all P < 0.0001). As measured by both lesion counts and a rigorous investigator assessment Estrostep was efficacious in the treatment of moderate acne vulgaris. Finally acne treatment with Estrostep resulted in a significant improvement in health-related quality of life. (authors)