The effect of academic stress on immune function, as measured by the rate of secretion of salivary secretory immunoglobulin A (s-IgA), was studied prospectively in 64 first-year dental school students. Perceived stress and s-IgA secretion rate were measured five times--during an initial low-stress period, three high-stress periods coinciding with major examinations, and a final low-stress period. The s-IgA secretion rate was significantly lower in high-stress than low-stress periods for the whole group. In addition, personality characteristics differentiated patterns of s-IgA secretion rates. Students characterised by a great need to establish and maintain warm personal relationships secreted more s-IgA at each point than did all other subjects. The s-IgA secretion rates of those with a high inhibited need for power continued to decline through the final low-stress period rather than recovering as in all other subjects.