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Surveys of Alouatta palliata. trabeata exsiting in the Ocú, Pesé and Parita communities (province of Herrera, peninsula de Azuero), Panama, were conducted from April to December 2001. I observed troops who were followed for several hours and repeatedly counted each time to confirm identification, age and sexual composition. I chose a strategic location surrounding the area (about 15 villages) of hedge and forest vegetation. During nine visits (five days per month), monitoring was conducted daily between 0600 and 1400 hrs. The direction from wish howling was heard was determined with the use of compass. Troop’s identifications were also helped by recording body markings on certain individuals, blonde hairs on the hands, feet and tail. I detected the presence of 119 howler monkeys forming part of five groups and calculated a total population about 261.8 individuals in 11 troops. Of 15 visited places, only three had howler monkeys and no other more. The tamarins’ monkeys (Saguinus geoffroyi) and capuchin (Cebus capucinus) have a high possibility to have been introduced on these areas. Population density was estimated at 0.017 troops/ha, and 40.5 ind/km². Mean troop size was 23.8 ranging from 15-39 individuals. Despite there being no reports of hunting by the local farmers there is a possible impact from the others communitie’s hunters. The howler population has been broken in to several groups as a result of cattle ranching.