Actually the answer is Yes. Yes, AAS start their effect immediately. However, it DOES take two-three weeks for you oil-bases to kick in. A basic chemistry lesson: AAS increase protein synthesis on a molecular level. Before the synthesis of a protein begins, the Amino Acids for the corresponding muscle protein "recipe" must be made. This is done through a process called transcription. The RNA molecule is produced and then this code is multiplied several times over. It is this process which is sped up by AAS. The next thing to occur is called RNA translation. This is where the "muscle code" is sent out to the manufacturer "the liver, etc." who then calls in the nutrients in the bloodstream into the cell so the muscle can be made. That was a super short lesson in something that would take 4-5 years of study. I will be happy to explain it in more detail if desired.