In nine children with the Laurence-Moon-Biedl syndrome a high incidence of nephropathy was documented. Renal involvement was noted in seven patients before or simultaneously with the diagnosis of LMBS. Five have uremia and two have died. All patients had an abnormal urogrum. The spectrum of renal lesions ranged from mesangial tissue proliferation to glomerular clerosis, interstitial scarring, and medullary and cortical cyst formation. A relationship between the lesions seen in the LMBS and those of other hereditary retinal-renal conditions is suggested.