Background: Although impaired sensory processing accompanies various clinical conditions, the question of its status as an independent disorder remains open. Our goal was to delineate the comorbidity (or lack thereof) between childhood psychopathology and sensory over-responsivity (SOR) in middle childhood using phenotypic and behavior-genetic analyses. Method: Participants (N = 970) were drawn from the Wisconsin Twin Project, a population-based sample of twins and their families. Mothers completed a sensory responsivity checklist when their offspring were on average 7 years old, followed by a diagnostic interview (Diagnostic Interview Schedule for Children; DISC) within 6-12 months. We examined the incidence of DISC diagnoses--attention deficit hyperactivity disorder, conduct disorder, oppositional defiant disorder, agoraphobia, general anxiety, obsessive-compulsive disorder, panic disorder, separation anxiety, social phobia, specific phobia, depression, enuresis, trichtollomaniatics, selective mutism, and pica--among children with SOR, and vice versa. Children with autism or pervasive developmental disorders were excluded from the present study. In addition, we examined parent-reported physical health diagnoses among nondiagnosed children and three groups of children with SOR and/or DISC diagnoses. Biometric models explored common underlying genetic and environmental influences on symptoms of SOR and psychopathology. Results: A majority of individuals who screened positive for SOR did not qualify for a DISC diagnosis (58.2%), and vice versa (68.3%). Children who screened positive for SOR only and typical children had similar rates of physical health problems. Turning to a dimensional approach, multivariate twin models demonstrated that modest covariation between SOR and DISC symptoms could be entirely accounted for by common underlying genetic effects. Conclusions: Our results suggest that SOR occurs independently of recognized childhood psychiatric diagnoses but is also a relatively frequent comorbid condition with recognized diagnoses. Genetic sources of this comorbidity are implicated.