Benzodiazepines are a group of related drugs which include diazepam (Valium) and alprazolam (Xanax). You will find information on the Benzodiazepines at http://www.drugs.com/xq/cfm/pageid_0...x/qx/index.htm All benzodiazepine drugs differ in duration of action, onset of action and potency. Diazepam is longer acting compared to Alprazolam which is shorter acting. Diazepam and alprazolam are both relatively quick in onset (useful for the treatment of anxiety). Alprazolam is also quick in offset often making treatment particularly difficult to discontinue. Alprazolam is more potent than diazepam on a per mg basis.