In immunologic studies of 20 children with severe facial birth defects, all were evaluated for quantity of T and B cells, immunoglobulins, and the third component of complement. Only 18 patients could be evaluated for blastogenesis and 16 for chemotaxis. Forty percent of the children had a decreased quantity of B cells. Eighty-three percent had a decrease in pokeweed-stimulated blastogenesis, and 75% showed decreased levels of one or more immunoglobulins. T cells were decreased in 60% of the patients, while 33% and 28% had decreased phytohemagglutinin-stimulated and concanavallin-A-stimulated blastogenesis, respectively. Chemotaxis was diminished in the polymorphonuclear leukocytes of 56% and the mononuclear leukocytes of 75% of the patients evaluated. The association of immune abnormalities and facial birth defects may be more common than in presently recognized.