Idiopathic hemihypertrophy is a congenital overgrowth disorder associated with an augmented risk for embryonal tumors. We present 4 cases of hemihypertrophy in Yemeni children living in Sana`a city. They presented to the outpatient clinics in a private hospital in Sana`a city, Yemen, over a period of 3 years from January 2009 to December 2011. The first 2 cases had no complaints apart from asymmetrical size of one side of their bodies (left side hemihypertrophy). The third case presented with left side hemihypertrophy and an abdominal mass, which upon referral to a cancer center was confirmed to be Wilms` tumor. The fourth case had overgrowth of the right leg and foot with polydactyly, and a right sided abdominal mass. He was diagnosed to have an ureteropelvic junction stricture with hydronephrosis and absent left kidney.