Data on cleft lip with or without cleft palate are utilized to evaluate a new method for estimating recurrence risk under the polygenic threshold model. The influence of critical factors on the accuracy of the estimated risks are evaluated. The model is relatively sensitive to the estimate of heritability employed and relatively robust to the population prevalence estimate and to family size. The calculated risks for cleft lip with or without cleft palate are contrasted with the empiric figures from studies on Caucasians and Japanese populations.