The antiproliferative and immunomodulatory effects of melatonin (MLT) have been demonstrated in a variety of neoplasms including colorectal cancer (CRC). In humans and other mammals, MLT acts on target tissues through membrane and retinoid nuclear receptors. The aim of this study was to evaluate transcription activity of melatonin receptors and genes associated with regulation of their activity in colorectal adenocarcinoma tissues in relation to clinical stage of cancer. A total of 24 pairs of surgically removed tumoral and healthy (marginal) tissue samples from colorectal cancer patients at clinical stages I-II and III-IV were collected. As an additional control, twenty normal samples were tak¬en from people whose large intestine tissues were reported as non-tumoral after colonoscopy. Expression of mRNA genes was studied by microarray HG-U133A analysis. The analysis of gene expression profile was performed using commercially available oligonucleotide microarrays of HG-U133A. High increase of MT1 mRNA expression levels in all cancerous samples vs non-cancerous tissues was observed. The MT2 mRNA expression levels increased slightly in marginal and malignant samples. Among the genes participating in the cascade of signal transfer in cells activated by MLT via melatonin receptors, we found encoding genes (GNA11, OXTR, TPH1) only for differentiating stage III - IV of CRC. Monitoring the expression levels of genes that are related to melatonin receptors may offer a strategy to anticipate tumour development and estimate the molecular changes that occur during carcinogenesis. The mechanism behind this association needs further elucidation.