Three clinical strains (isolates 1174, 1857, and 1937) of herpes simplex virus type 1 (HSV-1) were compared with the standard laboratory strain F of HSV-1 with respect to glycoprotein content in order to examine intratypic differences. Variation was demonstrated by radioimmunoprecipitation (RIP) with monoclonal antibodies to individual HSV-1 glycoproteins in purified virus particles and in infected cells. Compared with strain F, there was an increase in the concentrations of gC, gH, and gI in strain 1174, in gC and gH in strain 1857, and in gE and gG in strain 1937. The concentration of glycoproteins in purified virus particles from all strains was also compared to corresponding concentrations in infected cells by RIP. Levels lower in infected cells than in purified virus particles were observed for gG, gH and gI of the F strain, for gB, gC and gD of strain 1174, for gD, gG and gI of strain 1857, and for gC, gD, gE, gH and gI of strain 1937. The differences in viral protein processing and the heterogeneity observed in HSV-1 strains are discussed.