Serum IgA concentrations were measured in 1799 healthy Israeli military recruits (698 women and 1101 men) using an automated nephelometric system. The overall prevalence of IgA deficiency defined at a level of <50 mg/liter was 1.0 ± 0.46% (95% confidence limits). No significant difference was found between the sexes in the mean values of serum IgA. Statistically significant ethnic differences were evident. Recruits of European origin had lower serum IgA concentrations than the North African, Israeli, or Asian origin groups. Whether the apparently high prevalence of IgA deficiency in this young population in Israel has clinical significance is at present unknown.