Familial history risk factors in relation to autism were examined in a cohort of 164 autistic children referred to The Autism Center at New Jersey Medical School-University of Medicine and Dentistry of New Jersey, Newark, over a 2-year period (2001-2003). Information related to familial history was obtained from each family and reviewed by a clinician. It is shown that these families carry a higher overall burden of psychiatric and developmental illnesses compared to reported national levels. These families also carry a relatively high incidence of medical disorders, independently of developmental and psychiatric disorders. This work supports the underlying presence of genetic factors in the etiology of autism.