In this research, which investigated the quantitative histomorphologic development of the parabronchi and atria of lungs at 1. 3, 7, 15, 30 and 60 days old, 60 male quail were used. The interparabronchial septa were absent among the lung units which consist of parabronchi, atria and gas exchange tissue. It was observed that on the 1(st) day of hatching. the lungs had the same properties as adults and that there was no structural difference between the right and left lungs. The average diameter of atria rose according to the age and were 20.733 +/- 0.868 mu and 21.413 +/- 0.929 mu on the 1(st) day of hatching and 65.028 +/- 3.110 mu, 68.235 +/- 3.007 mu on the 60th day of hatching, in the right and left lung respectively. The number of parabronchi per unit area were 10.250 +/- 0.718 and 8.896 +/- 0.679 mu on the 1(st) day of hatching and 1.666 +/- 0.094 and 1.755 +/- 0.095 mu on the 60th day after hatching, in the right and left lung respectively. These values decreased in inverse proportion to age, but the average short and long diameters of parabronchi increased according to age. The difference between the diameters of, and the numbers of, parabronchi per unit area, and the diameters of atria of the right and left lungs, were not statistically. However, the effect of age on the above-mentioned parameters was statistically significant (p<0.01).