In the bioventing technique, soil vapor extraction (SVE) is used to promote aerobic biodegradation of contaminants in the vadose zone. Kinetics limited by mass transport of the contaminant and/or oxygen through the aqueous phase to the microorganisms and of contaminant to the gaseous phase may be expected during field operation. Sensitivity studies were performed with a one-dimension model for two substrates showing competitive inhibition, following Monod’s kinetics. The mass transfer limitations were represented by means of lumped parameters, and results for high and low values of these parameters were compared. Under kinetics severely limited by mass transport processes, biodegradation occurs at a rate given by the availability of dissolved oxygen, and important contributions of biological degradation to the overall cleanup are expected if oxygen is not utilized exclusively for the oxidation of other substances than the target contaminant. For relatively fast mass transport kinetics the system becomes quite sensitive to a rather large number of parameters, but important reductions in the remediation time will usually occur if high removal percentages are mandated.