The role of retinoids such as all-trans-retinoic acid (ATRA), 13-cis-retinoic acid (13-cis-RA),& synthetic RA analogs in mediating cell growth and differentiation has generated interest in their pharmacological utility for treatment of dermatological diseases, such as psoriasis and acne, as well as for oncological applications, such as chemotherapy and chemoprevention. Several retinoids, among them ATRA, 13-cis-RA, and etretinate are currently marketed for treatment of dermatological diseases and are experimentally being evaluated for cancer applications. Although these retinoids have proven therapeutically effective in the treatment of such diseases, their toxicities have limited and/or prevented their use for prolonged periods. As a result of recent discoveries regarding the biological function of retinoids and retinoid receptors, it is now possible to design compounds with improved therapeutic indices. In order to characterize novel retinoids it is helpful to prepare radiolabelled homologs. These labelled probes can be used to evaluate binding properties, pharmacokinetics, bioavailability and to identify metabolites.