Cancer is one of the major public health problems in our society. It is estimated that more than 18 million new cases are diagnosed worldwide every year; 280,000 in Spain. Incidence in following a growing trend. This epidemic could be controlled with research into new treatments and, above all, with adequate prevention. Primary prevention could prevent avoid up to half of all cases. For many others, secondary prevention is essential, as it make diagnosis possible in the stages of the disease when it is easily curable. These guidelines present the scientific evidence regarding secondary prevention in tumors in which its use is well-accepted: breast, cervical, colorectal, prostate, lung, ovarian, melanoma, and gastric cancer.