Jaen is the province with the greatest number of patients with lepra. This study analyzes the prevalence of the disease in Jaen during 1984 and 1985. At that time, all the patients known to the health and consume provincial delegation of Jaén were studied. The 305 patients included received a protocol aimed to study the different risk factors (age, clinical form, the people living together, socioeconomic standing, ethnic, etc ...). The disease shows to have a highly significant and special predilection in gypsies and it is located in a significant geographical area in the province. Lepra did not show a rural distribution, however it prevails in middle size urban nuclei. Although all patients belonged to a low social class, the disease did not show to exhibit any association among the ecology and the income per inhabitant.