The third follow-up survey associated with the High School and Beyond (HSB) Study was conducted during the spring of 1986. This report provides information that fully documents major technical aspects of the third follow-up sample selection and implementation, describes the weighting procedures, examines the possible impact of non-response on sample estimates, and evaluates the precision of estimates derived from the sample. The base year design is briefly reviewed. The possible impact of survey non-response is examined as a potential source of bias, and procedures for computing sampling errors and design effects are discussed. The 14,825 high school sophomores in 1980 and the 11,995 high school seniors in 1980 who were used in the second HSB follow-up survey were used in this study. The calculation of sample case weights that adjust for differential probabilities of selection and for non-response within weighting cells is addressed. Appendices include extensive tabulated data on sophomore weights and non-response adjustments, senior weights and non-response adjustments, and design effects and sampling errors. (TJH)