The transport, uptake and degradation of hydrocarbons by microorganisms has been a subject of interest for many years. The inherent low solubility of most hydrocarbons has been thought to be one of the limiting factors in the overall rate of degradation of hydrocarbons. The ability of surfactants to form micelles and increase the solubility of hydrocarbons to many times their normal solubility may overcome this limitation. Designed experiments with well defined surfactant systems of known phase behavior were done to investigate the effects of micellar solubilization by nonionic, ionic, and mixed nonionic and ionic surfactants on the degradation of n-alkanes by pure cultures of three strains of Gram-negative bacteria. It was found that solubilization by nonionic surfactants greatly increased the growth rates and accompanying oxidation of alkanes for two of the three bacterial strains. It also appeared, from initial experiments, that the inhibitory effect of the ionic micelles could be mediated by the addition of nonionic surfactants to form mixed micelles. A mathematical model that treated the solubilized alkanes as soluble substrates via a Monod expression with competitive enzyme interaction successfully described the experimental data. Nonlinear parameter estimation using a maximum likelihood method indicated that μ\sbmax was constant for a particular bacterial strain, and independent of surfactant concentration and alkane. The variation in observed growth rates was reflected in the variation of the K\sbs parameter which was found to be a function of surfactant type and alkane. The variation appears to represent differences in the rates of transport of the alkanes through the cell membranes.