Abstract. The fine morphology of the testes and epididymes collected from breeding Zebu (Bos indicus) bulls with normal or decreased testicular consistency (TC) at clinical palpation was studied. The ultrastructure of testicles with a slight to moderate reduction in consistency showed more obvious, albeit slight, degenerative changes in the seminiferous epithelium, with cellular debris present in Sertoli cells, compared with control animals. Abnormalities in the condensation of the chromatin and acrosomes during spermiogenesis were also common findings in cases of decreased TC. The cauda epididymides of these bulls did not show clear morphological deviations compared with controls, although the macrophagic activity of the epithelium was more pronounced, and cell debris as well as foreign cells were apparent in the lumen. The morphological findings confirm the relationship between a decreased TC at clinical palpation and the lowered normality of the testicular parenchyma, thus supporting the value of palpating scrotal contents as part of the field andrological clinical evaluation of breeding Zebu bulls in the tropics. Key words: Testicular consistency, Bos indicus, Ultrastructure, Testis, Epididymis.(J. Reprod. Dev. 45: [119][120][121][122][123][124][125][126][127][128] 1999) eef production in the tropics is based mainly on extensive production systems and natural ity [3] in European breeds under temperate conditions. A decrease in TC is commonly found in connection with acute or sub-acute testicular pathologies, such as testicular degeneration. Attempts to establish a relation between TC and seminal or fertility parameters of Bos indicus bulls have been inconclusive thus far [1,4], although morphological alterations of the seminiferous epithelium were more frequent in Zebu breeding bulls with low TC than in control bulls [5] and were often associated with temperature-induced testicular pathologies [6]. For Bos indicus, Bos taurus and crossbred breeding bulls extensively reared in Costa Rica, a negative relationship was found between decreased B mating. Under these conditions, it is essential that a complete clinical examination of the breeding bulls be made [1] and that clinical parameters related to the fertility of the bull be used as selection criteria for breeding purposes. One of these clinical parameters is testicular consistency (TC), which is normally evaluated while palpating the scrotal contents. Testicular consistency has been shown to be related to conception rate [2] and semen qual-