The dose response relationship to acitretin in five patients with Darier's disease was investigated. The patients received in the first 3 months 35 mg daily, and the dose was adjusted according to the clinical response. Four of the five patients showed a marked improvement with up to total clearance, although in two patients isomorphic reactions due to a relative overdose were seen. These isomorphic reactions improved with a reduction of dose. We suggest that treatment with acitretin is initiated at 10-25 mg daily with gradual adjustment of the dose.