A prospective clinical parametric study comprising women afflicted by breast cancer and otherwise healthy participants was undertaken. The mean plasmatic concentration of putative leucine amino peptidase and nucleoside diphosphate phosphotransferase enzymatic complex in breast cancer cases was significantly elevated [43.9 +/- 2.8 mug ml(-1) (n = 9)] when compared to those found in otherwise healthy women [8.07 +/-0.14 mug ml(-1) = 8)]. Women without images compatible with any tumours (n = 13) had a mean concentration of 10.77 +/- 1.49 mug ml(-1). The mean value obtained in women with fibroadenomas was 10.15 +/- 0.81 mug ml(-1) (n = 6) and with cystic fibrosis mastopathy 8.75 +/- 0.28 mug ml-(1) (n = 7). The efficacy of a tandem quantitative biodiagnostic system as a parametric screening tool for the early detection of breast cancer is underlined, raising the possibility of increasing the cost effectiveness of current imaging non-parametric technologies.