Data on respondent use of prescription and select over-the-counter (aspirin-containing and non-steroidal anti-inflammatory) medications were collected during the Wave IV in-home interview. The process of collecting the prescription medication data, therapeutically classifying the prescription medications, and structuring a file of the therapeutic classifications for dissemination to users is described below. The questions concerning use of aspirin-containing and non-steroidal anti-inflammatory medications are detailed in the Section 6 codebook of the in-home interview.