Interleukin-6 (IL-6) can stimulate a variety of tumors including prostatic carcinoma. Research has recently shown that IL-6 may act to stimulate the progression of prostatic cancer. To date, little research has been performed to better understand the nature of granulocyte macrophage colony-stimulating factor (GM-CSF) and the expression of IL-6. The aim of this study was to evaluate the effects of GM-CSF on the expression of IL-6 in prostate cancer-3 (PC-3) cells. The bone-derived PC-3 cell line was used in this study. Reverse transcription polymerase chain reaction (RT-PCR) and real- time PCR were performed to detect IL-6 mRNA expression. The IL-6 protein was measured by enzyme-linked immunosorbent assay (ELISA) after treatment with hGM-CSF. Our data indicated that IL-6 mRNA expression did not increase after treatment with hGM-CSF in comparison to the control group. However, the expression of IL-6 protein was increased compared to the control group. GM-CSF may modulate the post-transcription pathway of IL-6 expression in prostate carcinoma cells. Our data suggest that GM-CSF may have a role in IL-6-mediated development of prostate cancer.