Formulation development is key to the successful treatment of acne. There has been significant progress over the past few years, but not all developments can be universally applied. An effective topical formulation must provide chemical stability and enhanced penetration of active ingredients at optimal concentrations for efficacy and safety; be cosmetically acceptable; and not add side effects of its own. Both retinoids and fixed combinations containing benzoyl peroxide are commonly used to treat acne, but both have the potential to cause troublesome dose-dependent irritation and dryness. Excipients such as surfactants and alcohol have added to the problem. Two products have recently been introduced where a combination of micronization skills and well-chosen excipients has minimized irritation and dryness without compromising efficacy. Results from two major studies are discussed in this article.