Four fatal cases of chickenpox occurring during pregnancy are reported. Each patient died of characteristic diffuse interstitial pneumonitis. This complication of varicella has been described previously and, from the data available, it does not appear that there is any special susceptibility to disseminated chickenpox during pregnancy. At present, there is no drug therapy available which will cure the disease or modify its course once the lungs and other viscera are involved. Treatment is directed toward maintaining adequate pulmonary exchange and water balance until the disease resolves spontaneously. In none of these four cases did the infant survive.