This chapter provides insights into the application of artificial intelligence in diagnostic processes through various case studies. The chapter first explores the integration of artificial intelligence into diagnostic methodologies, including its role in differential diagnosis and clinical reasoning. Next, the discussion revisits traditional diagnostic techniques, such as the physical examination and phonocardiogram, and demonstrates how these methods are enhanced with artificial intelligence. The chapter concludes by examining specific medical domains, including general diagnostic performance, emergency department, radiology, pathology, cardiology, neurology, gastroenterology, psychiatry, telemedicine, and dermatology. These case studies demonstrate both the advantages and the limitations of artificial intelligence-based diagnostics.