In 42 fetuses and prematures, the entire mucosa from the rhinopharynx was stained by various whole-mount methods. The development, growth, spread, distribution, situation, and size of the glands were determined. The development starts in the 11th week below the tubal orifice, whence the glands spread to the entire rhinopharynx. The number increases gradually by about 60-70 glands a week. By the 23rd week, there are 1,100-1,200 glands in the rhinopharynx. After that juncture, there is presumably no further new formation. The density and size of the glands were at a maximum in Rosenmüller's recess, below the tubal orifice, and in the salpingopharyngeal fold, least anterior to the tubal orifice and at the junction to the pharynx. The role of the sero-mucous glands in the rhinopharynx under normal and abnormal conditions is dicussed.