This study investigated time trends and associated factors of incidence rates of diagnosed autism spectrum disorders (ASD) across the lifespan from 1995 to 2010, using data from the Danish Psychiatric Central Research Registry. First time diagnosis of childhood autism, atypical autism, Asperger's syndrome, or pervasive developmental disorder-unspecified (PDD-NOS) were identified, incidence rates were calculated, and data were fitted using non-linear least squares methods. A total of 14.997 patients were identified and incidence rates for ASD increased from 9.0 to 38.6 per 100,000 person years during the 16-year period. The increases were most pronounced in females, adolescents, adults, and patients with Asperger's syndrome and PDD-NOS.