I think it's B-6... It's not working for me, though. I take the entire B-complex, but it takes me forever to fall asleep every few nights, then I wake up anywhere from 3 to 6 a.m., can't fall back to sleep for anywhere from ten minutes to two hours. I am late to work every single day b/c my body will only wake up from 7:30-8:30 regardless of what time I go to bed... 10:00 p.m., 5:00 a.m., doesn't matter. I was tired all day until I started the B-vitamins, so now I don't fall asleep at work anymore at least. I know I suffer from sleep paralysis and obviously insomnia... I'm tired of it, literally. If it's any consolation to you, the B-complex really does help w/ daytime sleepiness. I tried caffiene, which was useless, but this really works... now if i could sleep at night....