Research shows that if you are a bodybuilder, interested soley in creatine's muscle-building abilities, you dont gotta worry. Caffiene will not interfere with creatine's muscle-building affects.

However, if you use creatine to aid in short bursting sprints (running, biking, basketball, etc.), then avoid caffeine. The way creatine assists in short-bursting anaerobic activity is through its ability to decrease "Relaxion Time" in the working muscle. (The time it takes for a muscle to return to its relaxed state after a contraction) By decreasing relaxion time, creatine helps prepare for the muscle for its next contraction more quickly. 400mg of caffiene throughout the daycompletely negates the positive effects of creatine in sprinting sports.