Objective To explore the relationship between the onset o f Panic disor der(PD) and the effects of parental age at delivery and birth order. Met hods Th e families of 75 probands with PD were studied by Haldane & Smith procedure. Results The development of PD was significantly associated with the parental age at delivery and birth order. Conclusion The older the parental age at delivery and the later the birth order, the more likely were the offspring to develop PD.