A patient with no family history of renal disease was referred for obstetric sonography because of elevated maternal serum and amniotic fluid alpha-fetoprotein (AFP), and was proved to be carrying a fetus with autosomal recessive polycystic kidney disease. Review of records of previous cases with a sonographic diagnosis of this disease revealed one other case with elevated and one case with normal amniotic fluid AFP. Sonographers should be aware of the potential diagnosis of this condition in patients with elevated AFP, even in gestations not known to be at risk. Because the sonographic diagnosis of this disease can be difficult in gestations known to be at risk, AFP determination may prove to be a useful diagnostic adjunct in these pregnancies as well.