Tourette syndrome and obsessive-compulsive disorder are neuropsychiatric disorders that have sparked considerable interest over the decades. They are the focus of research for a remarkable diversity of disciplines, ranging from neuroimagers and prenatal epidemiologists to experts in the neural circuits that connect the cortex with the basal ganglia, as well as neuroimmunologists focusing on brain-based autoimmune phenomena. Several hypotheses have been put forward to explain the onset and exacerbation of these illnesses. Here, we discuss the clinical phenomenology and treatment options that are currently available. New psychopharmacological agents are being used that are based on a greater understanding of the neurobiology and are being used in combination with behavioral interventions. Longitudinal clinical investigations into clinical symptoms and the natural course are providing additional clues on the underlying pathophysiology. Recent advances in research models are also reviewed in an attempt to clarify some of the molecular etiologies that lead to these disorders.