This list should enable you to offer a complete open bar for a 3-hour party with 20 guests. If your liquor cabinet already contains opened bottles of the items marked with asterisks, there's no need to buy more if the bottles are at least half full.

1 750ml bottle bourbon
1 750ml bottle Canadian whiskey
1 750ml bottle blended Scotch

2 750ml bottles London Dry Gin
2 750ml bottles vodka
1 or 2 750ml bottles of liqueurs, such as amaretto, Bénédictine,
 Chartreuse, Chambord, Frangelico, Irish cream or any other
 types your guests prefer
1 750ml bottle dry vermouth
1 750ml bottle sweet vermouth
4 to 6 750ml bottles dry white wine
3 or 4 750ml bottles dry red wine
24 12-fl.-oz. bottles beer
1 liter lemon-lime soda
2 liters cola
2 liters diet cola
6 12-fl.-oz. or smaller bottles ginger ale
12 12-fl.-oz. or smaller bottles tonic water
4 liters club soda
2 liters still mineral water
2 quarts orange juice
1 quart cranberry juice cocktail
1 quart grapefruit juice
1 quart tomato juice
20 to 30 lb. ice cubes or crushed ice