Behaviors of hungry female Anopheles gambiae were observed for 80 min in 13 cm diam x 122 cm long screened tubes having human breath piped in both ends. Paired trials tested a tube with an untreated net at both ends to a tube with an untreated net at one end and either a Permanet, Olyset or blank net treated with 400 mg a.i/meter² DEET at the other. Mosquitoes were either able to alight on the treated net, or prevented from doing so by means of a screen barrier. At the end of the trial, the treated net was replaced with an untreated net. Measurements included positions of living and knocked down females; numbers of sustained flights; contacts with the net after a flight; and mortality counts taken at least 16 hours post trial. DEET showed strong repellency. Mosquitoes showed excitation responses to both ITN treatments even in the absence of contact. Olyset nets caused low mortality, but repellency equal to DEET where there was contact. Permanet caused high mortality without repellency. These trials proved sensitive enough to show that in a closed system, there are differences between Permanet and Olyset; these differences indicated that whereas Olyset nets both deter and kill, Permanets function almost entirely as lethal traps.