DNA samples from 100 patients with cleft lip with or without cleft palate (CL/P) were compared with those of 98 unaffected control individuals with respect to transforming growth factor alpha (TGFA) genotypes. Among the Caucasians in this population (83 CL/P, 84 controls), there was a significant difference in the restriction fragment length polymorphisms (RFLPs) observed after digestion with TaqI (chi 2 = 4.68, P = 0.03). The frequency of the C2 allele in the Caucasian CL/P population was 0.169, whereas that in the control group was 0.089. When the data for Caucasians, African-Americans, and Asians were examined jointly, the chi 2 value for the pooled sample was 5.08 (P = 0.02). This confirms the hypothesis of Ardinger et al. [1989, Am J Hum Genet, 45:348-353] that TFGA itself or a closely linked gene contributes to the development of CL/P in humans.