In order to treat their clients successfully, psychiatrists must be able to make the most accurate assessment possible in each case. This work discusses the general principles behind psychiatric interviewing and assessment, then through the use of case histories combined with analysis, it shows how those principles apply in a variety of contexts. It shows how information is elecited from clients and used in forming assessments, how courses of action are decided upon, and how clients are reassessed as cases change and develop over time.