Preheat oven to 350°F. Lightly grease a baking sheet.
Stem the mushrooms. Reserve 1/3 to 1/2 of the stems and mince them.
Whip the cream cheese until smooth.
In a small bowl, combine the minced mushroom stems and crabmeat. Blend the cream cheese into the stem and crab mixture. Add garlic salt and mix well.
Stuff the mushroom caps with the cheese mixture.
Arrange the caps on the prepared baking sheet and bake for 20 minutes or until the mushrooms and crab mixture are hot and most of the liquid from the mushrooms has collected in the pan.