I smoked as late as 6pm the night before and used VALE 4X the following day and took the urine test around 2pm the same day and I passed.....the margin was narrow, but I passed...initially it was unclear, but given the 5 minutes the test is supposed to wait, the "line appeared" giving me a negative result...being that I have smoked non-stop for almost 20 years, VALE had it's work cut out, but it came through when I needed it!!! I "highly" recommend it! You do have to follow the directions about eating a dry meal 3 hrs before and drinking boatloads of water. After following the directions I allowed 2 hours for (as the product warns) "excessive urination" while I continued to drink water....then I immediately went to have the test performed. It cost $50 bucks total, which included a package of "pre" vitamins and the Detox drink....and it didn't taste too bad either!