The last year we fabricated some new immunosensors for the analysis of lactoferrin protein. In the present research the immunological and analytical characteristics of the immunosensor method have been extensively investigated. The study was therefore extended to cover the ability of the analyte and the corresponding antibody to produce the immunocomplex. A rough estimation of the K(aff) value was obtained at the midpoint of the Langmuir curve, where K(aff)=1/IC(50). The K(aff) value was found to be of the order of 10(6)M(-1). In addition we attempted in the present study to reduce the excessively long time required for each measurement, due to the fact that, in the previous researches the measurement procedure used was the classic "competition" ELISA type, employing an ad hoc enzymatic marker. One possible way of reducing measurement time was found to be to perform a kind of completely innovative "direct" measurement developed by us, which still uses an enzymatic marker and an amperometric transducer, as in the previous competition method.