Lacaziosis (lobomycosis) is a skin disease caused by Lacazia loboi, occurring naturally only in humans and dolphins. Attempts to culture the pathogen in vitro have been unsuccessful, and inoculation studies of lacaziosis development in mice have provided only limited, short-term data on the progression and propagation of L. loboi. The present study used photographic data from long-term photo-identification and health assessment projects to model and quantify the progression of lacaziosis lesions in 3 common bottlenose dolphins Tursiops truncatus from Sarasota Bay, Florida, USA. Dorsal fin images throughout each animal's sighting history were examined for lesion growth, and the proportion of lesion coverage in each photograph was estimated using image analysis tools in Adobe Photoshop. The progression of lacaziosis lesions and lesion growth rates were modeled using a non-linear monomolecular growth model. As data on lacaziosis development and advancement are limited in humans and laboratory animals, dolphins with a long-term case history of the disease may serve as a good animal model to better understand lacaziosis progression. Furthermore, this study demonstrates the utility of long-term population monitoring data for tracking the progression of a poorly understood disease that is relevant to both dolphin and human health.