You will have a timing issue when using a macro %let statement in a data step. The %let statement will get executed before the data step so it won't be part of the data step iteration and you also can't pass a SAS data step variable to the %let statement. There your "i" will simply be interpreted as the character 'i'. Not sure why you need a macro at all but as this is a code snippet reality might look different and there are good reasons for a macro. Below should make your code snippet work: %macro DefineInputArray;       ARRAY BYLINE(50) $16.  BYLINE1 - BYLINE50;    array iVal (50)    %do i=1 %to 50;      %let iter = %eval(1000+(&i-1)*1000);   iVALUE&iter    %end;     %str(;) %mend; data sims;   set data_inputs;   %DefineInputArray;   do i=1 to dim(BYLINE);    BYLINE = iVALUE;   end; run; ... View more