Abstract Objective: Cyclical trends in birth rates that vary from general population patterns have been reported for several neuropsychiatric disorders. These data are used to test etiological hypotheses. Monthly and seasonal variations have been demonstrated for Autism possibly implicating an environmental pathogenic factor. We analyse data from Israel, focusing on viral epidemics. Method: Data covering a 30 year period (1960–1989), including general population live births, autistic births, and incidence of viral encephalitis, viral meningitis, rubella, measles, and poliomyelitis were collected from Israel's Ministry of Health, Central Bureau of Statistics and National League for Autism. Periodicity and correlations between variables were analyzed. Results: Over the period studied, 290 autistic births were evaluated. Spectral analysis using the cosine function demonstrated a significant periodicity (tau) of 17.6 years ( P =0.011) and near-significant periodicities of 3.2 years ( P =0.07) and 4.1 years ( P =0.27). Superposition of these three periods showed a highly significant fit to the annual autistic birth pattern ( r =0.749, P =0.042). Multiple regression analysis of variables (encephalitis, meningitis, rubella, measles and poliomyelitis), yielded two significant findings: (a) during the period 1968–1989 the incidence of measles correlated with the rhythmicity of Autistic births ( r =0.49, P =0.036); (b) during the entire study period the incidence of viral meningitis correlated with this rhythmicity ( r =0.37, P =0.042). It is note worthy that the only risk factor demonstrating a cyclical trend was viral meningitis (tau=3.0 years, P =0.032). Conclusions: Cyclical trends are significant in Autistic births in Israel. Autistic birth patterns are partially explained by the rates of measles and viral meningitis in the general population. There is a statistically significant environmental association between autism and both viral meningitis and measles that should be further investigated.