The 2017 edition of The Top 100 Drug Interactions includes several hundred new drug-drug interactions and monographs. As in the past, we have included interactions that may produce clinically important adverse events based on their properties to assist you in predicting interactions were limited data are available. The table of CYP450 and drug transporter substrates and modifiers now includes over 500 drugs. In addition, many of the existing monographs have been revised to reflect newly published data. Interaction entries are easy to find in the index by either trade or generic name. The Horn and Hansten Drug Interaction Probability Scale is included to assess the probability of a causal relationship between a potential drug interaction and a patient event.