Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder characterized by mental retardation, obesity, retinal degeneration, polydactyly and syndactyly, diabetes mellitus, hypogenitalism, renal dysplasia and short stature. Definitive molecular diagnosis for BBS is not currently available and counseling of affected families is based on the 25% recurrence risk consistent with autosomal recessive inheritance. Our case presents the first successful use of second trimester targeted sonographic anatomy scanning to prospectively identify a fetus affected with BBS, and indicates that ultrasound can be of critical importance in providing precise as well as timely prenatal diagnosis for families at risk for this serious disorder.