The 4‐in. hydrogen bubble chamber has been used as a neutron spectrometer in the 5‐ to 30‐Mev region. A fast data‐reduction system for the analysis of the recoil‐proton tracks was developed, utilizing a commercial electronic coordinate‐measuring device, the IBM punch‐card system, and the IBM 650 digital computer. The resolution of the entire spectrometer system was determined by measuring the monoergic (14.1‐Mev) neutron spectrum from the t(d, n)He4reaction with different neutron collimators. The full width at half maximum of the measured peak was 10% of the peak energy.