Class I and II human leukocyte antigens were determined by a standard microlymphocytotoxity test in a group of 45 pediatric patients with selective immunoglobulin A deficiency (IgA-D), 33 of them with frequent respiratory tract infections, allergic diseases, or gastrointestinal disorders (RTIAG), and 12 with celiac disease (CD). The results showed that the DR1 allele, and the A1, B8, Cw7, DR3, DQw2; B35, Cw4, DR1, DQw1; and B14, DR1, DQw1 haplotypes could be involved with IgA-D susceptibility in RTIAG patients. Among the CD-IgA-D group, the B14 allele and A1, B8, Cw7, DR3, DQw2 haplotype were found to confer a high risk of developing IgA-D. A possible protective role may be postulated for DR2 and DR4 in both types of IgA-D patients. The present study confirms some of the previous findings in other white populations and describes new possible alleles and haplotypes that could be implicated with IgA-D susceptibility and resistance.