You can always string out panel data into one long observation for analysis. That way you avoid the homoscedasticity problems often associated with repeated measures analyses. You can look at the slope in one model (in GLM) using a TEST statement and coefficients that reflect the shape that you want to test (linear, here). This will only use complete observations. You can address the complete observation challenge (which is sounds like is substantial) with PROC MI to get a better estimate of the behavior than simple linear interpolation (which is what would happen if you used the within-subject slope). Doc Muhlbaier Duke ... View more