Two brothers have spermiograms with a similar pattern: absolute teratozoospermia with round-headed spermatozoa. The familial trait only has been previously one time in the literature. The spermatozoa show several abnormalities in the head. They lack acrosome and postacrosomal sheath. The nuclei are small and the chromatin is distributed in small groups. The nuclear envelope has abundant pores and is loosely attached to the chromatin. All the nuclei have brown inclusions, refringent when they are observed under the light microscope, vesicular and laminar under the electron microscope. Other abnormalities less frequently observed are: irregularities in the mitochondrial sheath, loss of parallelism of the dense fibres and duplication and angulation of the sperm tail. The hormonal assays and the biochemical tests are normal in both patients.