It is often claimed that general reduction, or diffuse loss, of perimetric sensitivity is an early sign of glaucoma. Our clinical experience and the results of a few other studies led us to believe otherwise. To investigate factors associated with diffuse field loss we reviewed 4222 Humphrey 30-2 threshold tests from 1582 eyes of 862 patients followed at our department. Most of these patients had ocular hypertension or glaucoma. Each field test was evaluated with the Glaucoma Hemifield Test of the Statpac 2 program. The Glaucoma Hemifield Test classifies field test results as within or outside normal limits regarding localized field loss and general shifts in sensitivity. General reduction of sensitivity without concomitant localized loss was found in 117 tests from 81 eyes of 69 patients. Corresponding patient records were found for 60 eyes of 60 patients. Media opacities or miotic therapy were noted in 46 eyes (77%), 10 eyes (17%) had end-stage field loss, and in 2 eyes (3%) other non-glaucomatous ocular pathology explained the diffuse loss of sensitivity. Thus, general reduction of differential light sensitivity as an isolated finding was almost always associated with reasons other than early to moderate glaucoma in this material mainly consisting of patients with glaucoma or increased intraocular pressure. Since only 2 out of the 1582 eyes had general reduction of sensitivity that was not explained by non-glaucomatous reasons, we conclude that purely diffuse field loss was not a sign of glaucoma.