DNA was extracted from varicella-zoster (VZ) virions prepared in sucrose gradients. Thirty-eight molecules examined by electron microscopy were found to have a mean length of 46.7 micrometers. Examination of self-annealed VZV DNA molecules revealed that the virus genome was composed of a unique linear large sequence with a mol. wt. of 74.4 X 10(6) to 78.4 X 10(6), and a unique short sequence of mol. wt. approx. 9.8 X 10(6) flanked by inverted repeat sequences of 4.7 X 10(6) mol. wt.