Background: Despite advances in acne therapy in recent years, treatment failures are common, especially in adult women. Spironolactone, an established androgen receptor blocker, is successful in treating adult women with acne, but side effects are common at the doses reported in published studies to date. Objective: The purpose of this study was to assess the therapeutic effect and tolerance of low doses of spironolactone used alone or as an adjunct in the treatment of acne in adult women. Methods: Records were reviewed from 85 women with acne treated consecutively with spironolactone 50 to 100 mg/day, administered either as single-drug therapy or as an adjunct to standard therapies. The maximum length of treatment was 24 months. Results: Clearing of acne occurred in 33% of patients treated with low doses of spironolactone; 33% had marked improvement, 27.4% showed partial improvement, and 7% showed no improvement. The treatment regimen was well tolerated, with 57.5% reporting no adverse effects. Conclusion: Spironolactone can be used in low doses as a single drug or as an adjunct to standard acne therapies in women with adult acne. When used in this fashion, treatment outcomes are favorable, and the drug is well tolerated. (J Am Acad Dermatol 2000;43:498–502.)