A total of 549 female, adult sheep, between 1 and 4 years old were tested for serum antibodies evidence of Mycobacterium avium subspecies paratuberculosis, using the absorbed enzyme-linked inmunosorbent assay (ELISA). Fifty one animal gave positive results to ELISA. Seventeen positive animals and three negative animals were necropsied. Gross lesions were recorded and samples for histopathological examination were collected fron ileocecal valve, ileum, jejunum, and mesenteric and ileocecal lymph nodes. Tissues were fixed un buffered 10 % formalin. Sections were stained with haematoxylin and eosin, and by the Ziehl-Neelsen method to detect acid-fast bacteria. Paratuberculosis lesions in ileocecal valve, ileum and jejunum were categorised according to a description of lesions associated with natural paratuberculosis in sheep. From an examination of 200 macrophages in eight fields (40x) of the mucosa with lesions of each sample tissue, were used to determinate the percentage of infected macrophages with mycobacteria. Eight fields of the same cells (100x) were observed to quantificate the mean number of mycobacteria per macrophage, grades as 0 (none), 1 (1-10), 2 (10-60) or 3 (>60). The relations between the serum ELISA optical densities values, the number of mycobacteria per macrophage, the lesion category and the body condition were analysed. The ELISA optical density range values 0.700 to 1.145, was divided into five equal intervals 1(0.700-0.789), 2(0.789-0.878), 3(0.878-0.967), 4(0.967-1.056), 5(1.056-1.145). The classifaction types of lesion of each tissue sample, the mean number of mycobacterias per macrophage and the body condition were asigned to their respective interval and the results are discussed.