Hormone-producing cells in the rat anterior pituitary gland are not randomly distributed; rather, there are specific topographic affinities among five cell types (Noda et al., Acta Histochem. Cytochem. 2001;34:313–319). In this study we reconstructed these affinities, at least partially, in primary monolayer culture. Pituitary cells collected from adult male rats were enzymatically dispersed and cultured for 72 hr at a density of 1 × 105 cells/cm2. We double-immunostained cells using antibodies against hormones, and then used confocal laser microscopy to examine the ability of the cells to attach to each other. We also statistically analyzed the affinity of all combinations of the five types of hormone-producing cells. We observed clusters by electron microscopy to identify junctional complexes between the cells. Confocal laser microscopy indicated that the features and attachment patterns of hormone-producing cells in vivo were similar to those in vitro. Statistical analyses revealed that the rates at which the five types of hormone-producing cells attached to growth hormone (GH)-, prolactin (PRL), and luteinizing hormone (LH)-producing cells were unequal, which suggests there are specific topographic affinities. The specific rates of adrenocorticotropic hormone (ACTH)-producing cell attachment to GH cells, LH to PRL cells, and PRL to LH cells were high, whereas that of PRL attachment to PRL cells was low. In addition, the rates correlated with the data from our previous in vivo study. Ultrastructural observations revealed few junctional complexes between hormone-producing cells. These results indicate that anterior pituitary hormone-producing cells can attach to specific types of cells by means of specific and/or nonspecific adhesion factors, and can reconstruct the topographic nature of the pituitary gland. Anat Rec Part A 272A:548–555, 2003. © 2003 Wiley-Liss, Inc.