FIELD TESTS of the effectiveness of the new insect repellent, diethyl toluamide, have been reported in recent years by Altman and Smith against Aedes spp. in Alaska (1) and by Gilbert and associates against Man8onia spp. in the Canal Zone (2), Aedes aegypti, Aedes taeniorhynchus, Aedes spp., and Psorophora confinnis, in Florida (3,4), and Aedes dorsalis and Aedes spp. in Oregon (5). Such test,s have usua,lly been based on the average protection time (the interva.l between application and first "confirmed" bite, that is, a bite followed by another bite within 30 minutes), and the ratio betwe,en the average protection time obtained with diethyl toluamide and that obtained with some "standard" formulation, either M-250 or M-2020. Results of these tests are summarized in table 1. The average pro,tection time afforded by formulations containing 50 percent or more diethyl toluamide wa,s more than 4 hours. In each of the tests shown in table 1, the treate,d area was confined to the forearm of volunteer test subjects in an att,empt to limit the high degre,e of variability inherent in this type of test, Travis (6) having proved that there were no significant differences in the results obtained on any of the limbs. Unfortunately, we assumed as poissibly other workers not thoroughly familiar with this test have, that the protection time based upon application of repellent to the forearm could be interpreted as the protection time to be expected for all exposed skin surfaces to which repellent was applied.