How effective is vsl#3 for ulcerative colitis, and how long should it be taken?

Probiotics and UC: Probiotics are often used as an adjunct to conventional treatment of ulcerative colitis, but they do not substitute for that treatment (whether "step up" or "top down" therapy). Probiotics can regulate gut flora, which is often disturbed when colitis is active or antibiotics are taken. If you have found a probiotic product that is well tolerated and comfortable to use, stick with it indefinitely.

Good data: There are good data on vsl #3. It is the most thoroughly studied of all the probiotics out there. The best results are in patients with uc who have had their colon removed and have a pouch. It is helpful in preventing pouchitis. Also studies suggest it may be moderately helpful on preventing flares in uc patients with colon intact. Still not useful as a standalone drug though.