Maggies Farm Roach Killer Gel Bait takes time as it has to be taken back to the colony and spread. Roaches can start dying within a few hours to longer. How long it takes to eliminate a roach infestation depends on how large the infestation is, how consistent and thorough you are being with treatments and what products you are using. There is not a set time; it can take but it can take weeks or months even to get complete control. Roach baits are typically not used alone but in combination with other products. We would recommend one of our roach control kits. You can see the kits by clicking on the link here. We also have a great article for eliminating them that can offer some great advice; you can find it here.