Among a very large number of preparations reputed to possess mosquito-repellent properties, only a few are really efficacious. The most commonly used preparations are those prepared with citronella oil. Definite information, however, on the comparative efficiency of many of these preparations is lacking. It was therefore our object to determine the value of different culicifuges under laboratory conditions. The experimental results obtained in this connexion are sufficiently promising to justify their publication, especially because owing to the war the want of an effective and a cheap culicifuge is all the more important.