Cutaneous leishmaniasis (CL) is common on the high plateaux and foothills of the Asir range in the south-west of Saudi Arabia and Yemen. In 1987 1198 and 1104 cases were reported among the Saudi populations of Asir and Al-Baha provinces, representing an estimated annual incidence of 12 and 38 per 10,000 respectively. The incidence rises from October to December, then declines to a minimum between May and August. The prevalence of Phlebotomus sergenti, a proven local vector in the highlands, is roughly in inverse proportion. Cases occur at all ages, over 60% have only a single lesion, and the head and neck are most commonly affected. Apart from a few patients who develop leishmaniasis recidivans, most respond well to sodium stibogluconate, or self-heal. Of 44 isolates typed by isoenzyme electrophoresis, 42 were Leishmania tropica belonging to 5 distinctive zymodemes. LON-72 (34 isolates), LON-73 (1), LON-71 (2) and LON-10 (2) were found at altitudes around 2000 m, 3 of them in a single village. Three isolates of LON-63 were found at altitudes between 600 and 1000 m in widely separated foci. L. tropica LON-10 and LON-71 have been isolated also from P. sergenti from highland foci. LON-72 failed to produce lesions in BALB/c mice and gave rise to only transitory lesions in the footpads of hamsters.(ABSTRACT TRUNCATED AT 250 WORDS)