I am trying to find observations that contain one word in a string but NOT another. For example, my observations look something like this: Diabetes mellitus Screening for diabetes mellitus Type II diabetes  History of diabetes Family history of type II diabetes Encounter for screening of diabetes mellitus   I want to return observations that contain 'diabetes' or 'Diabetes' but NOT 'Screening' 'screening' 'History' 'history' I tried what I thought the most intuitive way to do this would be: proc freq data=data; tables diagnosis; where find(diagnosis, 'diabetes') or find(diagnosis, 'Diabetes') and not find(diagnosis, 'History') or find(diagnosis, 'screening'); run; but obviously, this did not work and returned observations that DO contain History and Screening, ignoring the 'not.' Is the find function the best way to do this?    ... View more