Nurses who are involved in studies of tube feeding tolerance or who review the literature on this topic are confronted with a myriad of definitions and methods of reporting diarrhea. In a 1992 study, the authors reported that these definition differences influenced results. In a review of the current literature, they determined that little progress had been made toward standardizing definitions and reports of diarrhea in studies of tube feeding. A secondary analysis of stool characteristics of hospitalized patients using various definitions of diarrhea showed there was a positive association between stool frequency and consistency. Criteria for stool consistency in the definitions of diarrhea appeared to have a greater influence on diarrhea outcomes when stool frequency was low. The authors suggest recognition of a taxonomy of definitions of diarrhea in the absence of consensus, which will help guide the design of future investigations and facilitate the evaluation and utilization of research.