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Dear, SPMers I'm new in SPM and it's giving me a hard time. Currently I'm trying to do a 2-way repeated measure ANOVA in MRI study: two groups (experimental and control) and two time points (baseline and follow-up). I wanted to look at main effects for group and time, and an interaction effect between group and time. So I entered groups in this order: E1 E2 C1 C2. Contrasts that I entered for group, time and interaction were 1 1 -1 -1, 1 -1 1 -1 and 1 -1 -1 1 respectively. Time and interaction contrasts seemed okay but the group contrast of 1 1 -1 -1 indicated "invalid contrast". I couldn't figure out what went wrong in this design? (I used VBM2_ longitudinal data analysis toolbox designed by Christian Gaser) Can anybody help me and give me a tip on this problem? Ji-Youn Yi Research Assistant Department of Neuroscience Seoul National University, South Korea