Orientador: César Roberto Esper / Banca: José Domingos Guimarães / Banca: José Octávio Jacomini / Banca: Paulo Henrique Franceschini / Banca: Francisco Guilherme Leite / Resumo: O objetivo deste trabalho foi determinar o número de células luteais bovinas, comparando fêmeas taurinas com zebuínas no início e final do ciclo estral. Foram coletados corpos lúteos de 16 fêmeas sendo 8 taurinas e 8 zebuínas, distribuídas em 4 grupos sendo coletados os ovários nos dias 3 a 5 (2 grupos: taurino e zebuíno) e 16 a 18 (2 grupos: taurino e zebuíno) do ciclo estral. Os corpos lúteos foram processados para microscopia óptica e avaliouse as células luteais pequenas, grandes e intermediárias, quanto ao número celular, diâmetro, área e perímetro. Os animais taurinos apresentaram maior quantidade de células luteais pequenas que os zebuínos no início do ciclo estral (p<O,05) e final do ciclo estral (p<O,05). Registrou-se diferença nos valores médios do diâmetro, perímetro e área das células luteais grandes, pequenas e intermediárias entre animais taurinos e zebuínos, tanto no início quanto no final do ciclo estral. / Abstract: The aim of this work was to determine the number of bovine luteal cells comparing 80S taurus females with 80S indicus females at the beginning and at the end of estrous cycle. Sixteen corpus luteum were collected in eight 80S taurus cattle and in eight 80S indicus cattle, distributed into four groups. The ovaries were collected from the third and the fifth days (two groups: 80S taurus females and 80S indicus females) and from the sixteenth and the eighteenth days (two groups: 80S taurus caUle and 80S indicus cattle) of the estrous cycle. The corpus luteum was processed to optical microscopy and the small, big and intermediate-sized luteal cells were evaluated considering the number of cells, diameter, area and perimeter. The 80S taurus females presented a bigger amount of smallluteal cells than the 80S indicus females at the beginning of the estrous cycle (p,O,05) and at the end of the estrous cycle (p<O,05). The difference in the average values of the diameter, perimeter and the area of big, small and intermediate-sized luteal cells have been registered among 80S taurus cattle and 80S indicus cattle, at the beginning and also at the end of the estrous cycle. / Doutor