Complex Vertebral Malformation (CVM) is an autosomal recessive inherited defect in the Holstein breed. The defect has lead to structurally malformed calves and losses of pregnancies. To determine the effect of CVM on fertility in the Swedish Holstein Breed 375 Holstein bulls used in breeding by Svensk Avel and Skånesemin were assigned to this study. 228 bulls matched the criteria of birth year, 1995-1999, > 75 inseminations and a known CVM-status. Of the total 228 bulls 53 of them were CVM-carriers and 175 were non-carriers. The SAS-programme was used to determine the effects of CVM-status, the bull?s father and birth year on Non-return rates (NRR) for 28, 56 and 168 days.