Rhabdomyomata are the most common cardiac tumors in childhood and are associated with tuberous sclerosis. These tumors tend to regress in the first years of life. Little is known about their intrauterine growth pattern. We describe three fetuses with cardiac rhabdomyomata and illustrate the tumor growth by serial echocardiographic views during the second half of gestation. Tumor growth is proportional to cardiac growth and tends to be somewhat slower toward the end of pregnancy.