1. The conversions of pure cyclohexane and mixtures of it with varying amounts of thiophene have been studied under reforming conditions at 400–500° and 20–60 atm. on fresh, deactivated, and regenerated catalysts containing 0.5–10.0% of platinum on alumina. 2. On changing the temperature of the experiment from 400 to 500° while passing a mixture of cyclohexane with 1% of thiophene over a 1% Pt-Al2O3 catalyst, the content of methylcyclopentane in the catalyzates rises correspondingly from 8.3 to 29%, and the content of benzene increases from 3.4 to 42.1%. 3. Raising the pressure of the experiment from 20 to 60 atm. promotes an increase in the yield of methylcyclopentane both from pure cyclohexane and in the presence of thiophene. Thus, in the conversion of pure cyclohexane at 40 atm. and 500°, the catalyzate contains 37.3% of methylcyclopentane and 65.4% of benzene, while in the presence of 6% of thiophene the yields of methylcyclopentane and benzene under the same conditions are 57 and 9.3%, respectively.