Many of those with peyronie's disease suffer from ED (erectile dysfunction) as a result of their condition. It is of course healthy for all men to achieve erections on a regular basis, this is partly the reason why we have spontaneous erections, nocturnal erections and so on. L-Arginine is a precursor to NO (Nitric Oxide), which is required for erections to take place. Several studies have demonstrated an increase in the quality of erections from the use of L-Arginine.
L-Arginine is one of the cheapest supplements available and can be purchased from high street chains such as Holland & Barrett in the UK and numerous places abroad. For those looking for the best L-arginine supplement, San VasoFlow in a good option. It's popular in bodybuilding circles (provides a better "pump", more veined look etc) as well as fellow peyronie's patients where the benefit is increased bloodflow to the penis. Vasoflow is superior to many L-Arginine supplements due to its controlled release technology - so it stays in your system for longer. It is also coupled with L-Norvaline, which blocks the activity of arginase (promoting the conversion of arginine into nitric oxide). You could even combine Arginine with Pycnogenol , as studies have suggested powerful synergy between the two when it comes to treating ED.
This really is something that I would classify as a "must have", especially if you're in the active stage of the condition (as opposed to the chronic stage). L-Argine is sometimes used in combination with Pentoxifylline (Trental) and Viagra in what is known as the PAV cocktail. This treatment trio is recommended by some of the most respected peyronie's disease experts in the world (Dr Lue for instance).