In general, when a batted ball is ruled a foul ball, the ball is dead, all runners must return to their time-of-pitch base without liability to be put out, and the batter returns to home plate to continue his turn at bat. A strike is issued for the batter if he had fewer than two strikes. If the batter already has two strikes against him when he hits a foul ball, a strike is not issued unless the ball was bunted to become a foul ball, in which case a third strike is issued and a strikeout recorded for the batter and pitcher. A strike is, however, recorded for the pitcher for every foul ball the batter hits, regardless of the count.
A batted ball caught by a fielder in flight in foul territory is not considered a foul ball, but the batter is out and runners on base may advance at their own risk.
Rules vary from stadium to stadium for a ball striking the roof or suspended object in foul territory. Some consider such a ball to still be in flight, while others consider it a foul ball and dead from the time it strikes.
On rare occasions, such as in extra innings or the ninth inning of a tie game when a runner is on third base, fielders have been known to let long foul flies drop rather than risk losing the game on a sacrifice fly. Sometimes, in that situation, a fielder will not try to catch a ball that is close to the foul line in the hope that the ball will go foul at the last second--neither catching the ball nor letting it drop would prevent a defeat.
In different situations, a foul ball may be considered a positive or negative outcome of a pitch or swing. When there are zero or one strikes, a foul ball counts as a strike, benefiting the pitcher. However, a foul ball may reveal to the batter that he has timed a pitch well and need only make adjustment to the location of his swing on the next such pitch; this is often called a good cut or simply a good swing. Foul balls with two strikes are generally considered positive for the batter, since he thus avoids strike three on a potentially difficult pitch. Also, foul balls with two strikes increase the pitcher's pitch count, adding to his/her fatigue, thus providing some small advantage to the offense. A strategy of swinging on any ball to try to produce additional fouls and prolong an at-bat is often used against strong pitchers to try to drive them from the game sooner (and also the possibility of the pitcher throwing a pitch a hitter can get a hit on); this does, however, have the disadvantage of generating more strikeouts.