Surface area and volume measurements were made for ram and human spermatozoa. Measurements were made using different techniques in an attempt to confirm estimates arrived at by independent methodologies. Sperm head projected surface areas were calculated from published formulae using linear micrometry measurements or were obtained directly by image analysis. Total surface areas were calculated as twice the projected head area plus the flagella area, estimated from published dimensions. Spermatozoon surface area was also measured from electron micrographs using a stereological method. Micrometric methods gave values of 135 microns2 for ram spermatozoa and 106 microns2 for human spermatozoa. Stereology methods gave values of 142 microns2 for ram spermatozoa and 106.5 microns2 for human spermatozoa, offering good agreement between the two methods. Sperm volumes were estimated by stereology and by radiolabel volume exclusion methods. From stereology, ram sperm volume was 13.3 microns3 and human sperm volume was 22.2 microns3. From the volume exclusion method, ram sperm volume was estimated as 25 microns3. Attempts to measure total volume and water volume simultaneously using and adaptation of this method were unsuccessful. Separate estimation of water volume for ram spermatozoa gave a value or 12.8 microns3, suggesting a 50% water space. Results from this study are compared with existing published values.