Currently, there is only 1 published hot flash diary. This diary rates hot flash severity according to 4 categories: mild, moderate, severe, and very severe. The descriptions of these 4 severity categories are located on a separate form from the main data form. For each 24-h period, subjects record the number of hot flashes experienced for each of the 4 severity categories either by recollection or from a separate data source on which hot flashes have been tallied. This diary has been validated but does not conform to the FDA and EMEA guidance for industry. After we observed a high percentage of subjects reporting confusion when using this 4-category diary, we constructed and used a hot flash diary containing 3 severity categories that offered real-time recording of hot flashes, contained all severity definitions on the principle data form and also conformed to the FDA and EMEA guidance for industry. We compare these 2 diaries here and provide a sample of the 3-category diary, which has not been formally validated but is considered valid by the FDA and EMEA in support of drug approval. Either diary is acceptable for use in clinical trials.