The cancellations include the World Golf Championships American Express Championship in St. Louis, the PGA Tours Tampa Bay Classic, the Buy.Com Tours Oregon Classic and the Senior PGA Tours Vantage Championship in North Carolina.
American Express has corporate headquarters near the bottom of the World Trade Center in New York where two hijacked airlines plowed into both of the Twin Towers, causing them to topple.
This is the first time in five years that the Tour has even cancelled a single event. In 1996, the AT&T Pebble Beach Pro-Am was called off after 36 holes because of bad weather.
The events will not be rescheduled.
'The PGA Tour and its members on all three Tours, out of respect for the victims and their families of Tuesday's terrorist actions and in recognition of a national day of mourning to occur later this week, have determined that the best course of action is to refrain from playing our normal PGA TOUR schedule this week,' PGA Tour commissioner Tim Finchem said in a statement Wednesday.
The LPGA Tour said it would proceed with its 54-hole tournament in Portland. Commissioner Ty Votaw said the Safeway Classic would be reduced to a 36-hole event if a national day of mourning is ordered.
The Canadian Tour will play its Bayer Championship in Ontario. Players will wear ribbons in honor of those who died in New York and Washington, D.C.
Originally, officials planned to postpone first-round play. All four events were to begin on Friday, with the field in the American Express Championship playing 36 holes at Bellerive Country Club on Friday and 18 holes each on Saturday and Sunday.
The fields in the Tampa Bay Classic and Oregon Classic were first scheduled to play 18 holes on both Friday and Saturday, and 36 holes on Sunday once a cut had been made.