The Cr-Si-O material system is of interest for use in thin film resistors. The films are sputter deposited onto conducting substrates from metal-oxide compacts using various reactive gas mixtures. The cermet film compositions range from 50 to 100 vol.% SiO2 as determined from elemental measurements of the Cr, Si and O content. In a wide range of resistivities from 10 to 10(14) Ohm-cm measured through the film thickness, an apparent anomalous behavior is found as a function of the Cr, Si and O composition. The anomaly can be attributed to a discontinuous variation of resistivity with film composition near 80 vol.% SiO2. The film microstructure is characterized as a distribution of conducting metal-silicide particles within an insulating matrix. The 'effective medium' theory is used to predict the variation of conductivity and successfully models the anomalous resistivity behavior.