Squamouscellcarcinomaantigen(SCCag)isagroupofglycoproteinswithmolecularweight~45kDa,belongingtothefamilyofserine/cysteine-proteaseinhibitors(1).TheproteinwasoriginallyisolatedbyKatoandco-workersfromhumansquamouscellcarcinomatissueandshowntoconsistofatleast10subfractionsdifferinginisoelectricpoint(2).MorerecentstudieshaveshownthatSCCantigeniscomposedoftwodistinctbuthighlyhomologousgeneproducts,SCCA1andSCCA2withdifferentinhibitorspecificities(3).SCCantigenisaSEROlogicalMarkerofsquamouscellcarcinomasoftheuterinecervix,vulva,lung,head&neck,andoesophagus(4-6).Insquamouscellcarcinomaoftheuterinecervix,pre-treatmentserumSCCagmaybeusedasanearlystageprognosticfactor(7)andtheuseofpre-treatmentSCCaghavebeensuggestedinordertoselecthigh-riskpatientsforadjuvanttherapy(4).Further,forpatientswithelevatedlevelsofSCCagbeforestartoftreatment,theprofileofSCCagcorrelateswiththeresponsetorADIo-andchemo-therapyandmeasurementofSCCagmaythusbeusedtomonitortheeffectoftherapyandforearlydetectionofrecurrentdisease.