Resistant herpes simplex virus type 1 strains were obtained under the selective pressure of acyclovir, ganciclovir, bromovinyldeoxyuridine, foscarnet, 2-phosphonylmethoxyehtyl (PME) derivatives of adenine and 2,6-diaminopurine, 3-hydroxy-2-phosphonylmethoxypropyl derivatives of adenine and cytosine, and 2-amino-7-(1,3-dihydroxy-2-propoxymethyl)purine (S2242). The drug susceptibility profiles of resistant strains point to differences in the modes of action of PME and 3-hydroxy-2-phosphonylmethoxypropyl derivatives and common mechanisms of action of foscarnet, S2242, and PME derivatives against herpes simplex virus type 1 replication.