The study of the same people at several occasions is known by various names: panel studies, multi-wave, multi-variable models, cohort analysis, and gain score analysis. The use of econometric concepts, path analysis, and structural equation analysis to study multi-wave, multi-variable models became widespread in methodological practice in the late 1960's. This paper examines alternative procedures for analyzing a two-wave, one-variable model. The situation studied occurs when a dependent variable and a set of independent variables are measured on the same group of people at two times. The use of multiple regression and structural equation modeling are compared in models with and without measurement error. Two different strategies for studying dependent variables are considered: first, the use of the difference or gain score as a single dependent variable, and secondly, the recursive use of the Time 1 and Time 2 data together. The LISREL structural equation approach is used to analyze data which resulted from a joint effort in 1977 and 1978 of the Federal Reserve Bank and the School District of Philadelphia to study factors affecting the reading achievement of 1,800 elementary school children. This data was reported in "What Works in Reading." (Author/RL)