Normal human spermatozoa carry either the X or the Y chromosome. The differences between X and Y spermatozoa (X and Y haploid cells) may exist in two areas: the different chromosomes (i.e. different kinds and numbers of genes) and the different sperm structures and functions (i.e. different genetic expression). The aim of this study was to determine whether there are any size between X and Y spermatozoa and whether sperm size and shape varies between men. Identification of the Y (and X inferred) status of individual spermatozoa was carried out by polymerase chain reaction (PCR), amplifying the putative testis-determining gene (SRY) together with a control gene (ZP3). PCR amplification of 871 out of 895 (97.3%) single motile spermatozoa showed that 444 (51.0%) were Y and 427 (49.0%) were X-bearing spermatozoa. Of 233 normally-shaped but immobilized spermatozoa, 217 (93.1%) were photographed and measured. Statistically, the length, perimeter and area of the sperm heads, and the length of the sperm necks and tails of X-bearing spermatozoa were significantly larger and longer than those of Y-bearing spermatozoa. Some peculiarities (or variations) in the X and Y sperm shape and size in individual donors were found. The pre-screening by micro-measurement of these specific haploid characteristics of individual spermatozoa in different donors, which may be closely related to their different genetic conditions (or diseases), may be important in human medicine and animal husbandry, especially in sperm prefertilization diagnosis.