A field measurement was obtained of tire inflation practices representative of typical automobile drivers. Approximately 2000 vehicles were surveyed during a midsummer period, and 400 vehicles during a midwinter period. Inflation pressures covered a wide spectrum with 10 percent being at least 6 psi below manufacturer's recommendation and 10 percent at least 3.5 psi above. During the summer, an average of one tire per vehicle was underinflated by 3 to 6 psi. The winter survey indicated that an average underinflation of 5 to 8 psi was present. A general conclusion is that the typical vehicle has at least one tire in which underinflation could cause serious tire deterioration and substantial increase in the rolling resistance and corresponding fuel usage.