A histochemical and ultrastructural study of the testes, epididymides and spermatic cords from 6 adult men with amyloidosis secondary to several diseases is described. Amyloid fibrils, consisting mainly of AA protein, were deposited in the walls of blood vessels of the testis, epididymis and spermatic cord, as well as in the tunica propria of the seminiferous tubules. The seminiferous epithelium showed slight hypospermatogenesis. Many Leydig cells exhibited unstained 'bar' or 'arc'-shaped cytoplasmic areas similar to the cholesterol deposits of Leydig cells in adrenoleukodystrophy.