This study uses the multiple logistic regression method to estimate the effectiveness of seat belts in reducing fatal and nonfatal injuries to occupants involved in motor vehicle crashes. Two vehicle groups - passenger cars, and other passenger vehicles that included vans and pickup trucks - were considered in estimating seat belt effectiveness values using highway crash data in Kansas. According to the results, the estimated effectiveness of seat belts in reducing fatal injuries is 56% for passenger car occupants and 61% for others. In passenger cars, seat belts are 53% and 55% effective in reducing incapacitating and non-incapacitating injuries, respectively. In the case of other passenger vehicles, corresponding values are found to be 52% and 51%.