Tyrosine hydroxylase (TH) positive juxtaglomerular neurons in the olfactory bulb consist of at least two groups with different soma sizes. On the other hand TH positive neurons are known to be generated continuously in the postnatal and even adult periods. We investigated the birth dates of small- and large-sized TH positive juxtaglomerular neurons. 5-Bromo-2'-deoxyuridine (BrdU) was injected at various developmental and juvenile stages and BrdU-labeled neurons were examined in adult mice. We revealed that both small- and large-sized TH positive neurons were generated at embryonic and perinatal periods and that TH positive neurons generated at the juvenile period were small-sized but not large-sized juxtaglomerular cells.