Abstract: A particular uncommon isomer of retinoic acid (namely 11-cis-retinoic acid, or neotretinoin) is useful in treating conditions involving abnormal cellular differentiation and hyperproliferation, such as psoriasis. A new method of synthesizing this isomer, in quantities that has allowed it to be compared therapeutically with the more commonly available all-trans and 13-cis isomers, is presented. As measured on the inventor's own psoriasis-affected skin, topical treatment with 11-cis-retinoic acid is much more efficacious in reducing symptoms and has substantially reduced side effects, as compared to topical treatment with the other isomers. A single application of a 0.001% neotretinoin cream to psoriasis lesions leads within 48 hours to substantial amelioration of associated dermatological symptoms, including itching, scaling, bleeding, and abnormal appearance.