In the present case-controlled, retrospective study, we have revisited the relationship between MBL and ovarian cancer with an entirely separate series of patients and controls in order to confirm or refute the apparent paradox (association with genetic MBL deficiency, but not serum MBL deficiency) reported earlier, and we have supplemented our investigations to include MASP-2 concentrations, MASP2 genotyping and MBL–MASP-1 complex activities. This evidence concerns the gene MBL2 and mannose-binding lectin deficiency.