Supercritical fluid (SCF) reaction media have been previously shown to facilitate heat removal and heavy product extraction from catalyst active sites in a variety of heterogeneous catalytic reactions, such as Fischer-Tropsch synthesis (FTS). This work explores the feasibility of using SCF media to enhance methanol-to-hydrocarbons (MTH) reaction performance relative to traditional, gas-phase operation. Conversion of methanol over H-ZSM-5 was carried out in a continuous fixed-bed reactor in the presence of supercritical isooctane. Isooctane was selected as the SCF medium primarily because of its low reactivity over H-ZSM-5. The performance of SCF-assisted MTH was compared with that of gas-phase MTH at both 300 and 370 degrees C. Relative to gas phase operation at the same conditions, the use of supercritical isooctane resulted in improved catalyst maintenance and increased hydrocarbon productivity with increasing time on stream.