The green peach aphid, Myzus persicae (Sulzer), is found worldwide in temperate, subtropical and tropical areas attacking tobacco crops. Two field experiments to evaluate the efficacy of some aphicides were carried out in 2001 at the Tobacco Research Institute farms in Scafati and Bovolone, on highly aphid-susceptible Burley (cv. S2/95) and Virginia Bright (cv. BTMS21) lines, respectively, with the support of the E.U. Tobacco Research Fund and the Italian Ministry of Agriculture (Tob-Res-Info 96/T/18 project). In both experiments a randomised complete block design with four replications was used. Aphid population was estimated by counting live individuals on the upper 4 leaves of 15 plants/plot for a period of 72 days at Scafati (8 observations) and 78 days at Bovolone (11 observations). Aphid infestation degree was rated on a seven-point scale (where 1 = absence of aphids; 2 = 1-10 aphids; 3 = 11-50 aphids; 4 = 51-100 aphids; 5 = 101-500 aphids; 6 = 501-1000 aphids; 7 = more than 1000 aphids). Infestation scores were re-expressed as natural Logs or on a 0-100 interval scaled on the local maximum observed score. At Scafati, except for the imidacloprid-seedbed, all treatments showed a good degree of control (85% to 98%). Among the water-setting treatments, thiamethoxam and imidacloprid showed comparable efficacy, while in the spray treatments imidacloprid was superior to acetamiprid and pymetrozine. Among the treatments consisting of one application, actara-setting and imidacloprid-setting were better than imidacloprid-seedbed. At Bovolone, where infestation was extremely low up to the first week of July increasing suddenly afterwards and peaking at the end of the month, setting-water treatments were more effective than imidacloprid+oil, which was slightly better than imidacloprid and acetamiprid-standard. On the whole, the highest aphid control was obtained with soil watering treatments and the lowest with the single spray before transplanting. Soil watering treatments seem to combine both high efficacy and economy of use, thanks to a reduced number of applications.