In order to test for the presence of primary infections by multiple herpes simplex virus-1 (HSV-1) strains and the simultaneous reactivation of multiple strains in latent HSV-1 infections, viral clones isolated from 12 viral strains shed into saliva of malignant patients without herpetic lesions and from 10 viral strains obtained from the herpetic focus were analyzed by DNA cleavage patterns. In asymptomatically shed viral strains, only 1 of 12 strains (8.7%) had different clones. In infectious viral strains, all clones of 10 viral strains showed the same cleavage patterns in each strain. These results suggest the existence of simultaneous reactivation in multiple latent HSV-1 infections.