ABSTRACT:The immunoglobulin classes of the sperm‐agglutinating antibodies in the seminal fluid and serum from four vasovasostomized men, as well as in operatively obtained testis‐epididymis fluid from two of them, were investigated by specific solid‐phase absorption of IgG, IgM, and IgA. In two patients the major part of the seminal agglutinins was IgA, and in one IgG, indicating that both local production and diffusion of sperm agglutinins from serum to the testis‐epididymis compartment may take place. The total levels of immunoglobulins in seminal fluid generally increased after the operation, and IgM was present in two postvasovasostomy samples. This suggests a pathotopic potentiation effect of the vasectomy on the epithelial lining of the testis‐epididymis compartment. Comparison of the results of solid‐phase absorption with anti‐IgA and antisecretory component (SO pointed to the presence of “free” SC in postvasovasost