OBJECTIVE There is increasing evidence for the role of cytokines in pituitary differentiated function and tumorigenesis, but the spectrum of cytokines found in the pituitary is unknown. Therefore profiles of cytokine expression were determined in different human anterior pituitary adenoma sub‐types.DESIGN The reverse transcriptase‐linked polymerase chain reaction (PCR) was used to identify the presence of cytokine mRNA within human pituitary adenomas.PATIENTS Seventeen pituitary adenoma biopsies removed at transsphenoidal surgery were examined: 4 somatotrophinomas, 7 non‐functional adenomas, 4 prolactinomas, one case of Cushing’s disease and one case of Nelson's syndrome.MEASUREMENTS RNA was extracted from each adenoma biopsy and reverse transcribed into cDNA. This was specifically amplified in a PCR using oligonucleotide primers complementary to each cytokine. The cytokines investigated were interleukin (IL) ‐lα, IL‐lβ, IL‐2, IL‐4, IL‐5, IL‐6, IL‐7, IL‐8, tumour necrosis factor (TNF)‐α, TNF‐β and transforming growth factor (TGF)‐β1, β2and β3. The products of each PCR were visualized using agarose gel electrophoresis.RESULTS All 17 adenomas expressed IL‐8 transcripts, but no expression of IL‐2, IL‐5 or IL‐7 was found. IL‐6 was expressed in all 4 somatotrophinomas, 3 of 7 non‐functional tumours, 2 of 4 prolactinomas and in the single case of Nelson's syndrome. At least one of the 3 isoforms of TGF‐β was found in all but 2 tumours; one prolactinoma and one non‐functional adenoma. IL‐1α, IL‐β, IL‐4, TNF‐α and TNF‐β were expressed sporadically by individual adenomas.CONCLUSION These data suggest that whilst IL‐8 may be important, the local expression of the cytokin