Internal table looping problem.

Hi all,

i have a prob in looping internal table.

i want to copy some fields of itab to itab1 but onlly those fields where Material type is 'XXX' , 'YYY' , 'ZZZ'.

i have tried it by doing

loop at itab where mtart = 'XXX' or 'YYY' or 'ZZZ'.

but its not working ..

is thr any other way of doing this if yes then plz help me out...

thanxxxxx......