ELISA (double-determinant) was used to detect the serum isoferritin (SIF) levels in 42 patients with nasopharynx cancer (NPC), 38 with lung cancer (LC), 26 with esophageal cancer (EC) and 89 with other cancers, a total of 195 cases (151 males and 44 females). The results revealed that the positive rate of SIF in patients with cancer was 73.8% (144/195), among which, the positive rates in patients of stage I-II, stage III-IV, in patients not operated upon and in those after operation were 64.8%, 81.3%, 81.4% and 63.4%, respectively. Statistics was significantly different in SIF level between the stage I-II and III-IV groups, and between the un-operation and after operation groups (P < 0.001) by rank sum testing. The positive rates of NPC, LC and EC were 73.8%, 86.8% and 73.1%, respectively. The results have demonstrated that isoferritin is a malignant neoplasm associated antigen, and SIF level is related closely with the development of the tumor and operative treatment.