I can attest to DE working on bedbugs. About a year ago, I suddenly found my small single-apartment unit infested with them - it was insane! From what I could gather, mine was a fairly 'heavy' infestation. Both the physical and psychological affects on me from these parasites, was enough to almost push me over the edge; no fooling. After doing careful research online for possible ways to get rid of them, I first tried a couple of 'traps' (including a yeast trap) but to no avail. Then I tried the DE. I made use of an empty dish washing-liquid bottle, (for the spout-tip), and filled it with the DE so I could "spray" the powder into every crack and crevice by 'squeezing the DE-filled plastic bottle. I then applied a "moderately thick" dusting over the carpets. Lastly, I dusted my mattress on both sides, and made sure it got into every mattress seam, etc. - then covered the mattress on top with a plastic sheet which draped down the sides but did not touch the floor. (I also disposed of all my old bedding, just to be sure.) The first application, I just left for about 2-3 days, (btw, I'd already noticed that it seemed to be working at this point). Then I vacuumed it all up, making sure that the vacuum cleaner contents were properly disposed of, and I even cleaned all the hoses, nozzles of the vacuum completely afterwards; then did an equally thorough re-application of the DE. About 2 more days went by, & 'no more bedbugs'! I wanted to make absolutely sure, so I did another vacuuming/ re-application. All together, it was maybe 5-7 days, total, and they were completely gone... for good. This stuff is a God-send, in my opinion. I used the Safer brand from Ace Hardware, as well. *.Note: another thing I found out while I was doing this, was that Windex (or rather, 'ammonia window cleaner') was great for if I actually came across a living bedbug... one light 'spritz' of the ammonia mist would instantly immobilize and kill them on the spot, I discovered.