This report documents the results of a full-scale, field lateral load testing program conducted at two sites in Washington state. The sites were chosen to represent soil conditions WSDOT geotechnical engineers commonly encounter and for which little information on the response of laterally loaded piles was available. One site consisted of a deep deposit of soft silt in which 18-inch diameter piles were being installed for replacement of an existing bridge. The other site consisted of a moderately deep deposit of peat that was suspected of causing foundation movements in an adjacent bridge structure. Full-scale, field lateral load tests were performed on two instrumented piles at each site. A high degree of consistency was observed between the results of the two tests at both sites. The test results indicate that, for the loading conditions imposed during the tests, the response of the soil to lateral pile movement can be described by the Integrated Clay Criterion previously developed by researchers at the University of Houston. Integrated Clay Criterion parameters for the soils at each site are developed from interpretation of the test results.