We have compared the reliability of the information about drug therapy and pregnancy retrieved by interviewing patients with that distilled from pharmacy records. In the initial phase of each interview we used the internationally accepted open-ended technique, and extended this with an indication-oriented set of questions and then a set of specific drug-oriented questions. These data were then compared with those from pharmacy records on dispensing for the same patients during their pregnancy. The results suggest that if drug consumption during pregnancy is evaluated by interview, one should not restrict oneself to open-ended questions but should include indication-oriented and, when appropriate, drug-oriented questions. Such specific questions offer the opportunity of detecting the use of over-the-counter medication and of constructing drug use/complaint profiles. By contrast, pharmacy records will give better information in case of long recall periods and in patients with multiple and/or repeated drug use. Investigators should use the complementary elements of both techniques where appropriate.