Semen for use in artificial insemination must be of good quality. To satisfy this demand we have to be able to predict the quality of semen from individual donors. Statistical analyses of data on 3,418 ejaculates from 87 donors demonstrated that each donor’s ejaculates could be characterized by a lognormal distribution of the sperm concentration, the concentration of motile spermatozoa before freezing and the concentration of motile spermatozoa after thawing. Furthermore, the ratio of the concentration of motile spermatozoa before freezing to the total sperm concentration and the fraction of motile spermatozoa surviving the freezing procedure were found to be constant for individual donors. Based on these observations a statistical quality control scheme for the selection of donors and for the continuous control of semen quality is presente