Seminal proteins (IgA, IgG, albumin) were measured in normozoospermic patients and in patients with normozoospermia associated with agglomerations of spermatozoa. The type of agglomeration was not taken into account. A slight yet significant increase in seminal IgA was detected in patients with agglomerations whereas the other proteins remained unchanged. By testing seminal plasma against C1q by double diffusion it was shown that many patients of both groups had nonimmune C1q precipitins. The significance of such precipitins in semen is not known.