Thirty-nine mentally normal unrelated children diagnosed as having febrile convulsions were included in this study. The following have been carried out: (a) detailed anamnesis and clinical examination; (b) cerebrospinal fluid investigation; (c) EEG examination between attacks; (d) HLA-antigen determination; (e) estimation of serum IgA, IgG, IgM; and (f) counting of percent spontaneous E-rosette formation. The results were statistically compared to normal Egyptian controls. The results could be summarised as follows. (1) Only HLA-B5 antigen frequency is high among patients (xc2−19.1,P<0.0001). Relative risk is 4.4 which shows significant association (WY2= 29.145,P<0.0001) and etiologic fraction equals 0.377. (2) The means of IgA and E-rosette in the patients were significantly low (t= 3.46,P<0.01 andt= 3.92,P<0.001, respectively), (3)HLA-B5 is the only antigen with high frequency among the two groups of patients with low IgA and E-rosette (xc2= 11–9 and 18.2, respectively). (4) There is a significant association between B5 and low IgA(P0.05). The suggestion is that the genetic control of febrile convulsions is in linkage disequilibrium with HLA-B5, low IgA and low total T-cells. This altered immune function in otherwise normal children with febrile convulsions may predispose them to acute infections and high fever which precipitate convulsions.