Formation of multipolar nuclear spindles in spermiocytes has been demonstrated in three highly in-bred and closely related bulls with a type of testicular hypoplasia which can be summarised as arrested spermiogenesis. The spindle abnormality can be assumed to be the cause of the disturbance in spermiogenesis and to be associated with the formation of characteristic giant cells in later stages of spermiogenesis and their presence in the ejaculate. The ejaculate is watery and the centrifuges sediment contains giant cells with two to more than ten flocculent nuclei as well as solitary pyknotic nuclei and a few sperm with normal morphology. Two of these bulls had served more than twenty times; according to the breeder one bull produced two calves in spite of his oligospermia. Multipolara karnspolar i spermiocyterna har pavisats hos tre starkt inavlade och narbeslaktade tjurar med en typ av testikelhypoplasi som narmast kan karakteriseras som ‘arrested spermiogenesis’. Karnspoledefekten formodas vara orsak till rubbningen i spermiogenesen och sta i relation till forekomsten av karakteristiska s. k. jatte-celler i senare stadier av spermiogenesen och i ejakulatet. Ejakulatet ar vattnigt tunt. Spermacentrifugatet karakteriseras av jatteceller med tva till c:a ett tiotal karnor med flockigt innehall, oftast placerade i mitten av cellen, pyknotiska karnor och enstaka spermier oftast med normal morfologi. Tva av tjurarna ha vardera utfort c:a 20 betackningar, varvid den ena tjuren enligt uppgift lamnat 2 draktigheter, trots att den var behaftad med oligospermi.