Using a scoring rubric based on RUSA’s Guidelines for Behavioral Performance of Reference and Information Service Providers, librarians’ performance in 106 chat reference transcripts in which a patron was determined to be acting inappropriately were compared to 90 randomly chosen transcripts from the same time period in which no inappropriate behavior was identified. Librarians serving appropriately behaving patrons scored significantly better on two of five major dimensions of the RUSA Guidelines. Recommendations for librarians serving inappropriately behaving patrons and for improving the three of the five major dimensions are given.