A breakaway of four riders including Adam Hansen of T-Mobile Team was reeled in shortly before the finish in Santa Rosa.

Riders involved in the crash lost several minutes, but the race officials decided to credit most of them with the winner's time, meaning that Leipheimer retained the leader's jersey.

This decision, which meant extending the "safety zone" to 6 miles (10 km) before the end, was criticized by some riders and team staff.

Reigning Olympic and World Champion Paolo Bettini captured Stage 4, the event's longest stage, edging Gerald Ciolek, Juan José Haedo, and Thor Hushovd in a sprint finish after the peloton reeled in a seven-man breakaway consisting of Hilton Clarke (Navigators Insurance), Aaron Olson (T-Mobile Team), Kirk O'Bee (Health Net–Maxxis), Alejandro Acton (Colavita–Sutter Home), Christophe Laurent (Crédit Agricole), Lucas Euser (Slipstream–Chipotle), and Sean Sullivan (Toyota–United).

Yellow jersey holder Levi Leipheimer extended his lead over second place Jens Voigt and the rest of the field.