This chapter focuses on the two main psychiatric categories through which doctors described mental illness: diagnoses and symptoms. It analyses them not as “objective” clinical data showing from what the patients admitted to the institutions were suffering, but as pointers of psychiatric theory and practice, the physiognomy of the patients, the conditions that led to psychiatric hospitalisation, and the social use of psychiatric hospitals. The chapter is structured around the clarification of the psychiatric terms used in the Eginitio and the Dromokaitio. Each section centres on a group of diagnoses, while the last section presents an overview of the main symptoms recorded in case histories.