The authors examined the prevalence and clinical correlates of pathological laughing and crying (PLC) using the Pathological Laughter and Crying Scale (PLAC) in 92 consecutive patients with acute symptoms 3, 6, and 12 months after traumatic brain injury (TBI). The prevalence of PLC during the first year after TBI was 10.9%. Compared to patients without PLC, patients with PLC had significantly more depressive, anxious, and aggressive behaviors and had poorer social functioning. Additionally, PLC was associated with the presence of anxiety disorder, and focal frontal lobe lesions, especially in the lateral aspect of the left frontal lobe. Findings revealed that prefrontal regulation of limbic circuits may be involved in the pathophysiology of this disturbed emotional expression.