This multicenter, randomized, double-masked, parallel-group study assessed the efficacy, safety, and tolerability of azelaic acid 20% cream compared with those of its vehicle for the treatment of facial hyperpigmentation in darker-skinned patients (phototypes IV to VI). Following a 24-week treatment period, azelaic acid produced significantly greater decreases in pigmentary intensity than did vehicle as measured by both an investigator's subjective scale (P = 0.021) and a chromometer analysis (P = 0.039). There was a significantly greater global improvement with azelaic acid than with vehicle at week 24 (P = 0.008). Azelaic acid produced a slightly but significantly greater amount of burning (weeks 4 and 12, P < or = 0.046) and stinging (week 4, P = 0.002) than did vehicle. At the end of the study, more patients treated with azelaic acid than with vehicle reported having much smoother skin and being very satisfied or satisfied with their treatment. Also, more patients treated with azelaic acid than with vehicle rated their medication as being more effective or the same as past treatments. Thus azelaic acid is an effective and well-tolerated treatment for hyperpigmentation in darker-skinned patients.