SummaryLevels of soya protein‐specific IgE were measured in a normal adult population (seventy‐four males, fifteen females) who ingested soya‐containing and control diets during two 4‐week periods. Increases in soya‐specific IgE were observed for some individuals following ingestion of the soya‐containing diet, and for the female group the increase in soya‐specific IgE was statistically significant (P= 0·02). The increase of soya‐specific IgE was small and led to lower levels than that associated with adverse effects. The increase in soya‐specific IgE in the female group was accompanied by a significant increase (P= 0·02) in total immunoglobulin A. Changes in the level of soya‐specific haemagglutinating antibody, soya‐specific IgG, IgA and IgM as measured by ELISA and the immunoconglutinin titre could not be related to ingestion of t