A high-throughput vapor-phase catalytic experimentation unit with 15 parallel microreactors and fast, on-line GC product analysis was built. The 15 open tubular microreactors were mounted in a single furnace and fed with a common gas stream. Decane hydroisomerization experiments were conducted on 35 mg quantities of reference platinum-loaded ultrastable Y zeolite particles at 200 degreesC, 4.5 bar, using a hydrogen/hydrocarbon molar ratio of 375/1 and contact times of 100-800 kg s/mol. The microreactor outlets were sampled sequentially. GC analysis of the C-1-C-10 alkane product mixtures was achieved in 3.2 min with a multi-capillary column. The actual gas flow rates and contact times in the individual microreactors were derived from the GC FID signals after dilution of the reaction product stream with a calibrated hydrogen gas flow. The maximum temperature difference among the microreactors, measured in an empty reactor unit was ca. 6degreesC at 200degreesC. The conversion data were in excellent agreement with a kinetic model established for a conventional reactor. Fitting of the kinetic data obtained in the individual microreactors; to the model confirmed the small temperature variations depending on the location of each microreactor in the catalyst furnace.