Our previous work demonstrated a 300% augmentation of serum etretinate concentrations when the drug was administerd with milk rather than with water. We have begun a maintenance study to determine whether the clinical course of patients (proriasis, Darier's disease) is altered by the mode of drug administration. We have investigated whether isotretionoin concentrations area affected by coingestion of milk. We have begun collection of data on the persistence of etretinate in patients of treatment.