WASHINGTON — In the days leading up to President Obama’s trip to Europe, the director of the Secret Service, Julia A. Pierson, sat down with the agency’s senior officials to reiterate a message she had focused on during her first year in the job.

Although it had been nearly two years since several agents were caught soliciting prostitutes in Cartagena, Colombia, shortly before Mr. Obama arrived there for a summit meeting, Ms. Pierson said the agency remained under scrutiny. Agents should be reminded, she said, to be on their best behavior during the coming trip to Europe, where Mr. Obama planned to meet with European allies.

Despite her efforts, the agency and Ms. Pierson, who was traveling with the president on this trip, are again confronting embarrassing behavior by agents.

On Sunday, the day before Mr. Obama arrived in the Netherlands, three agents were sent home by the Secret Service in connection with excessive drinking. One of the agents was found passed out in a hotel hallway after he could not figure out how to get into his room.