Numerous photoactivatable dyes have been proposed as photodynamic therapy (PDT) candidates during the past few years.Very few will ever graduate to approved drug status.Critical issues exist postresearch which can be factored into the selection of suitable photosensitizers for development and substantially enhance prospects of success.Examples are provided by the novel porphycene family of synthetic dyes.Non-research factors such as patents, regulatory agencies and finance require early consideration.Porphycene photosensitizers have been designed chem. to ensure purity, avoid isomers, offer rapid metabolism, minimize phototoxicity and enhance target tissue selectivity while addressing key issues of safety, efficacy and economics in the development of a topically-applied photosensitizer for dermatol. disease.