Abstract
A trigger is the starting point of problem-based learning (PBL) cases. It is usually in the form of 5-6 text lines that provide the key information about the main character (usually the patient), including 3-4 of patient's presenting problems. In addition to the trigger text, most programs using PBL include a visual trigger. This might be in the form of a single image, a series of images, a video clip, a cartoon, or even one of the patient's investigation results (e.g. chest X-ray, pathology report, or urine sample analysis). The main educational objectives of the trigger image are as follows: (1) to introduce the patient to the students; (2) to enhance students' observation skills; (3) to provide them with new information to add to the cues obtained from the trigger text; and (4) to stimulate students to ask questions as they develop their enquiry plan. When planned and delivered effectively, trigger images should be engaging and stimulate group discussion. Understanding the educational objectives of using trigger images and choosing appropriate images are the keys for constructing successful PBL cases. These twelve tips highlight the key steps in the successful creation of trigger images.