The birthdates of substance P-positive neurons in chick dorsal root ganglia (DRGs) were determined by a combined immunohistochemical-autoradiographic method. Both substance P-positive and -negative neurons in lumbosacral DRGs were born between days E3 and E6 in ovo. Substance P-positive neurons were born relatively late in comparison to other neurons in the DRG, but did not have unique birthdays.