Hello Anastasia, I did not use proc PANEL but I looked into documentation and found the following line: "The response variable on the left side of the equal sign is regressed on the independent variables listed after the equal sign." It relates to MODEL statement of the procedure. It means that it is necessary to create a variable, say bc=B*C in your Panel dataset and then use MODEL A = B BC /FIXONETIME; SIncerely, SPR ... View more