Also note, macro language merely substitutes for &VAR to generate a SAS language statement.  Your SAS program includes:   if yes = 'yes' then set lib1.base_1; Hopefully, if you saw this statement in your program you would realize that it does the wrong thing.  (This also explains why SAS sees the need to create a variable named YES.)     The solutions already suggested are best.  But recognize that you could also get the right result (but at the cost of a longer-running program) by adding double quotes:   if "&var" = 'yes' then set lib1.base_1; This would generate a clumsy but workable program containing: if "yes" = 'yes' then set lib1.base_1; ... View more