Neurotensin, a neuropeptide growth factor, and its two specific neurotensin receptors, NTSR1 and NTSR2, were shown to be expressed by human B cell lines. Another NTSR, sortilin, which is common to neurotensin and neurotrophins, was also detected as we have previously described. Neurotensin was functional in B cell lines; it induced their proliferation and inhibited apoptosis induced by serum deprivation or Fas activation. Quantitative study of gene expression in two malignant B cell diseases showed that NTSR2 was overexpressed, NTSR1 decreased, and neurotensin was unexpressed in B cell leukemia patient's cells, as compared with healthy B cells. However, these expressions did not significantly change in large diffuse B cell lymphoma lymph nodes compared with benign ones. This study points out that neurotensin and its two specific receptors are expressed in human B lymphocytes. Such expressions were not described, and their relationship in B cell diseases, especially in chronic B cell leukemia, needs to be considered further in regard to these findings.