The relationship between serum IgE and castor bean (Ricinus communis)-specific IgE was studied in a group of dockworkers and other residents of Marseilles who were diagnosed as having castor bean allergy. The diagnosis was made because they had asthma or other allergic symptoms together with a positive skin test to castor bean. Total serum IgE was found to be higher in castor bean-allergic patients (mean = 174 IU/ml) than in a control group of local blood donors (mean = 66 IU/ml). IgE levels were not as high as those found in the sera of a previously identified group of castor bean-allergic dockworkers from Port Sudan (mean = 902 IU/ml). Castor bean-specific IgE was demonstrated in the serum of 91% of the allergic group and there was some correlation with total IgE (r = 0.53, p <0.01). The proportion of IgE antibody specific for castor bean was determined in 20 castor bean-sensitive patients using the radioallergosorbent test and was found to vary between 9 and 64% (mean = 38% or 265 ng/ml). No castor bean-specific IgE antibody was detected in the control group.