L:-arginine definitely has some effects. Before HGH was isolated, l-arginine was used therapeutically and as an HGH challenge before testing HGH blood levels. It is a precursor to nitric oxide in the body which is why it can have a vasodilating pumping effect. Taking before bed on an empty stomach it will increase gh secretion. It won't make you huge but can contribute to some muscle building and fat burning effects. You will also notice that you will sleep much deeper. It won't help you fall asleep but once you are asleep, you will sleep very soundly. In fact if you take too much or do not allocate enough hours for sleep, you may end up being overly sleepy in the morning. Be careful with long term use as other memebers have mentioned, it can increase prolactin levels and alter other hormones which are all in a delicate balance.