Insulin Like Growth Factor (IGF I) as the one of the strongest growth factors which can affect cancers development including colorectal cancer. IGF I induces processes of the cells growth and division. It regulates cells cycle and inhibits apoptosis. There is limited data about correlation between IGF I and staging of the tumor.The aim of the study was estimation of the clinical usefulness of IGF I concentration in the serum of the patients with colorectal cancer.Material and methods. We have examined 125 individuals with colorectal cancer. The age range was 36 to 92 years. They have been operated in the 2nd Departament of The Gastrointestinal Surgery of the Medical University in Białystok. Serum concentration of the IGF I have been estimated using immunoassay ELISA before and after operation. Correlation between serum level of IGF I and clinicopathologic features: age, gender, localisation of the primary tumor, TNM stage of tumor, histological type and histological grade (G) of the cancer have been estimated.Results. Our study revealed statistically significant increased serum concentration of IGF I in patients with locally advanced colorectal cancer (pT3 and pT4) comparing to less advanced (pT2) The investigations showed higher serum concentration of IGF I in patients with poorly differentiated cancers (G3) than in moderately differentiated. Similarly higher serum concentration of IGF I were found in male, in patients older than 60 years and in mucigenous colorectal cancers.Conclusions. Our results indicated that IGF I can be one of the factors of the prognosis in colorectal cancer development.