Clonazepam is not just any regular Benzodiazepine, it's actually classified as a chloro-nitrobenzodiazepine because it is a chlorinated derivative of nitrazepam. But back to your original question, if anything, the chemical clonazepam itself actaully lowers libido. But as Captain.Heroin said, it is an anxiolytic, but that also possesses muscle relaxant among other common benzodiazepine properties. I believe that your experience is either a placebo effect, which I'm leaning more towards, or it is just lowering you inhibitions/performance anxiety (as mentioned previously). Another possible reason is that you do have very bad anxiety where your body is in a constant state of "alert" or more commonly known as "fight or flight", in this state your body "pulls" the blood away from the extremities to allow more oxygen/etc. to the vital organ's and other bodily systems. So maybe now that your not constantly on edge, and your body can calm down, your blood is flowing freely causing your erection lol. Trying to be all scientific but the word erection makes me giggle.