The 35 adenohypophyses of the White Leghorn cocks were prepared for this study. Relationship between the cell types and the affinity of dyes was investigated with microspectrophotometrical method. Results obtained in this study are as follows: 1. Basic four cell types, acidophils, basophils, amphophils and chromophobes, have been distinguished in the pars distalis of the domestic fowl by cytological observation. Basophils of the two types, light and deep, and chromophobes are similarly distributed in both the cephalic and the caudal lobe. Amphophils are confined in the cephalic lobe and two types of acidophils, orange and red, are found only in the caudal lobe. Acidophils are well stained by acid dyes, such as orange G or acid fuchsin. By microspectrophotometry, they are subdivided into two types. The absorption maximum of the cytoplasmic granules stained with those dyes has been observed at the wave length of 480 mμ in one group of acidophils, whereas in the other group has been observed at 543 mμ. 3. Basophils are well stained by basic dyes, such as methyl green or methyl blue. Two types of basophils, light and deep, can be distinguished obviously with PAS-Matsuo tetrachrome stain. Cytoplasmic granules of the light basophils show the absorption maximum at the wave length of 634 mμ, but the granules of the deep basophils show a peak at the wave length of 560 mμ followed by the maximum absorption at 634 mμ. 4. Amphophils are violet or purple in color with the Matsuo-tetrachrome stain. Absorption spectra of the cytoplasmic granules in these cells show that these cells are well stained by acid and basic dyes simultaneously. Three peaks of absorption were recognized at the wave length of 543 mμ, 480 mμ and 415 mμ followed by the maximum absorption at 634 mμ. 5. It was shown that the microspectrophotometrical observations provided more detailed informations in the discrimination of adenohypophyseal cell types than usual histological methods. PAS-Matsuo tetrachrome staining was the most suitable among nine staining techniques used in the present study.