A polymerase chain reaction (PCR) assay that identifies and differentiates wild-type(wt)and vaccine strains of varicella-zoster virus (VZV) was used to determine if VZV strains with restriction fragment length polymorphisms resembling those of the Japanese Oka vaccine strain were present in thewtpool outside of Japan. Virus samples (n= 114) from patients with chickenpox and zoster from various parts of the United States and Australia were analyzed. The assay correctly identified 113 samples aswtstrain. The 1 sample identified as Oka vaccine strain came from a child with leukemia who developed a vaccine-associated rash after receiving the live attenuated varicella vaccine. At this point, there is no evidence thatwtstrains resembling the vaccine are circulating outside of Japan. This indicates that this PCR assay can be utilized to distinguish rashes due to vaccine andwtVZV.