This is a population-based case-control study of the risk factors associated with the transmission of Andean cutaneous leishmaniasis (uta) with a concurrent design comparing persons who developed uta against persons who did not. Cases and controls were matched by age. sex and place of residence. The unit of analysis was the person . The main exposure groups were: characteristics of the house, environmental characteristics around the house, and behaviour patterns of people. The study was carried out in five endemic regions of Peru. 187 cases and 335 controls were admitted to the study. Using matched and conditional logistic regression, in study areas of Lima & Ancash (region 1) and Piura (region 2) Departments we have identified risk factors which imply that transmission occurs (a) inside houses, (b) outside but close to houses, (c) around houses, but not clearly indoors or outdoors, and (d) away from houses. In region 1 we found three risk factors of type a, using a kerosene lamp (OR=6.6. c.i.:2.2-19.7), having a chimney (OR=4.9, c.i.: 1.9-12.5) and living in a stone house (OR=2.9, c.i.:1.6-5.2), one of type b, cutting wood (OR=7.4, c.i.:2.1-26.4), and three of type c. living in a house > 30 m from road (OR=3.9, c.i.: 1.4-10.7), with a vegetable garden (OR=2.8, c.i.: 1.1-4.1) and living in a house having > 6 persons (OR=4.2, c.i.:l.9-9.7). In region 2, we found four risk factors of type c, living in a house having an earth floor (OR=2.3. c.i.: 1.1-4.7), with cows (OR=1.3, c.i.: 1.1-1.6) and a neighbouring vegetable garden nearby (OR=2.9, c.i.:1.3-6.9), and living > 30 m from a river (OR=3.3, c.i.:3.1-8.4), and one of type d. doing irrigation work at night (OR=2.2, c.i.:1.2-4.2). The variability of risk factors between regions 1 and 2 can be explained by differences in (i) the frequency of exposures and (ii) the importance of factors. We conclude from OR's and PAR'S that much transmission occurs around houses. Certainly, some transmission is indoors: the population attributable risk for factors associated with indoor transmission in region 1 was 79%. suggesting the possibility of uta control by preventing biting in houses. It remains questionable how much transmission goes on outdoors
