<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by 0524:
On Wednesday night at Yankee Stadium, Kevin Appier was averaging 47 seconds between pitches. The game lasted 4 hours and 11 minutes, concluding at 12:31 a.m. What's the Major League Baseball rule, if any, for time allowed between pitches?</font>
From Major League Baseball Rules - on MLB.com
Rule 8.04
"When the bases are unoccupied, the pitcher shall deliver the ball to the batter within 20 seconds after he receives the ball. Each time the pitcher delays the game by violating this rule, the umpire shall call "Ball." The intent of this rule is to avoid unnecessary delays. The umpire shall insist that the catcher return the ball promptly to the pitcher, and that the pitcher take his position on the rubber promptly. Obvious delay by the pitcher should instantly be penalized by the umpire."
Since Appier had people on base most of the time, there would be no rule about those situations. And I've also never seen this rule enforce.