The relationship between oral temperature and serum IgA and IgG antibody responses to Shigella sonnei infection was examined in 65 experimentally infected adult volunteers. Although the IgA antibody response appeared to correlate directly with the rise in oral temperature following infection, stepwise regression analysis revealed other associated signs and symptoms as the critical elements underlying this apparent correlation. There was no evidence of a positive correlation between the IgG antibody response and the peak increment in oral temperature after infection. Although published data obtained in vitro suggest that fever might have a potentiating effect on antibody production, no such effect was seen in human volunteers with acute shigellosis.