This works great for gnats. It catches dozens every day. But it only catches an occasional house fly, even when 50 are flying around the house. I've tried it in many different locations, made sure no other light is on any where in the house. It will catch 1 or 2 flies only. I added dry cat food to lure the flies, and now it catches 4 or 5 house flies. But I live in a farming area, and have 20 flies at a time flying in my house in the summer. For me, this just isn't good enough results.
I purchased this to deal with a fruit fly infestation and it's been in place now for about a week with barely noticeable effectiveness. There are a few fruti flies stuck on the board but a significant number more still flying around. I am going to engage a professional externinating service. Save your money.