At present plasma tissue inhibitor of metalloproteinases-1 (TIMP-1) is undergoing validation as a biological marker in colorectal cancer (CRC). The clinical implementation of plasma TIMP-1 in prognosis, prediction, screening and monitoring CRC requires robust information as to the influence of preanalytical factors, including inter- and intrapersonal biological variations. The aim of the present study was to evaluate the possible effects of smoking on the level of TIMP-1 in plasma from healthy subjects.