Sobriety checkpoint roadblocks are used to detect and deter drunk drivers. When a car is stopped at the roadblock, the driver is asked to produce a valid driver's license and a vehicle registration. The initial stop and search of a vehicle is not based on probable cause. A Missouri case, in which a driver was stopped at a sobriety checkpoint roadblock, found to be intoxicated, and later arrested, is discussed in detail. The defendant claimed the sobriety checkpoint violated his fourth amendment rights. The court held that in Missouri sobriety checkpoints are not unconstitutional per se. The manner in which police conduct a sobriety checkpoint influences its constitutionality. State and U.S. Supreme Court cases outlining constitutionally acceptable procedures for conducting roadblocks are discussed in detail. It is important for law enforcement officials to promote the public interest while limiting the degree of intrusion on motorists. 120 footnotes.