We demonstrate the feasibility of laser-induced phosphorescence thermography for gas-phase temperature field measurement in a high-pressure cell. BaMgAl10O17:Eu (BAM) was used as a thermographic phosphor; it shows a blue-shifted laser-induced emission spectrum with increasing temperature. Local temperature was determined from the intensity ratio of two disjunctive emission bands. A new seeding device was developed to suspend the solid thermographic phosphor particles in a gas environment. The particle suspension time was modeled and validated by experiments. The influence of multiple scattering and other aspects of quantitative measurement were examined. The technique is currently capable of measuring up to 650 K, limited by signal intensity. The 2D temperature distributions were measured with a precision better than 60 K at 650 K. Multiple scattering limits the spatial resolution to only about 10 mm along the line of sight.