Telomerase is expressed in almost all human malignant processes but not in benign and normal tissues, with the exception of germline and stem cells. Because of its prevalent expression and potential as a target for cancer therapy, telomerase is the subject of intense investigation, and numerous papers have been published. We present the most recent findings on the association between telomerase activity and human malignancies, recent developments in methods of telomerase detection, telomerase utility in monitoring of patients with cancer for residual or recurrent disease, and potential usefulness of telomerase in treatment of cancer.