&NA;Twenty‐five pituitary adenomas were analyzed for expression of various chromogranin/secretogranin (Cg/Sg) messenger RNA (mRNA) transcripts by in situ hybridization (ISH). An additional five adenomas were also analyzed by Northern hybridization. Immunohistochemical staining for CgA and for SgIV (with monoclonal antibody HISL‐19) was also performed. Most prolactin and adrenocorticotropin adenomas did not express CgA mRNA or protein, whereas growth hormone (GH) tumors had low to moderate amounts of CgA mRNA by Northern and in situ hybridization analyses and were focally positive for CgA protein. CgB, SgII, SgIII, and SgV mRNA transcripts were present in most adenomas, and SgIV protein was detected in all groups of tumors. A GH and a null cell adenoma cultured for 7 days also expressed CgA/Sg mRNA transcripts and protein. Paraffin sections of some adenomas that were negative for CgA protein had detectable CgA mRNA by in situ hybridization analysis. These results indicate that CgA mRNA and protein are more commonly expressed in glycoprotein hormoneproducing tumors compared with other types of pituitary adenomas and that ISH for CgA may detect the mRNA transcripts for CgA even when CgA protein is not detected by immunohistochemistry.