The fertility profile of 307 Thai male volunteers whose wives were currently in early pregnancy was established by genital examination, semen analysis and serum hormone analysis. Ninety percent of the subjects had testicular volumes of 12-25 ml (mean 17.2 ml) which was found to relate to body weight, height and the ponderal index as well as to the sperm count. However, values for semen analysis were significantly below the recognised standard for Caucasian males. There was an inverse relationship between testicular volume and the serum concentration of FSH, LH and prolactin. It is suggested that a common protocol for male fertility assessment should be used to establish standard parameters for racially different male populations.