My understanding is that 5-HTP is the intermediate biochemical in the body between tryptophan and serotonin. Tryptophan is in some foods like turkey and Brazil nuts, and our bodies turn it into 5-HTP, which is then turned into serotonin. L-tryptophan was the supplement version of tryptophan, but apparently had some unpleasant side effects so it was pulled. www.5-HTP.org has some good info about it. I have had good luck with 100 mg of 5-HTP on an empty stomach about an hour before bedtime. I sleep more restfully and am happier when I wake up. I understand it's good to start with 50 mg and see if that works, and add more if needed. If I run out and don't get more for a few days, I start having more insomnia and sadness within a few days. Also, it took a few days to take effect, but has been well worth it and no side effects.