Fifty-seven herpes simplex virus strains, isolated from ocular herpes, were screened by complement fixation, seroneutralization and thermosensitivity tests. They were distributed as follows : 44 type 1, 3 type 2, 7 intermediate type ; 3 had a type 2 thermosensitivity and a type 1 neutralization. Discrepancies in these results, with the three tests, show that there is, in each typed group, strains of virus which react differently, and this could indicate a continuity from one type to another. As the strain progressively reacts more like the type 2, clinical symptoms become more severe. In a certain number of cases where several simultaneous or successive samples were performed, there was a hypothetic possibility of change in the behaviour of herpes simplex virus strains in the eye.