Operation of fixed bed reactors with periodic flow reversal as proposed by Matros and co-workers is an unconventional mode of operation for exothermic, equilibrium limited catalytic reactions. In the present paper, reverse flow ammonia synthesis at 240-300 bar over a promoted iron catalyst is considered. The catalyst had a particle size of 1.0-1.5 mm to neglect the intra- and interparticle transport intrusions. Temperature profiles, which developed and moved back and forth through the laboratory scale reactor, depending upon the direction of the flow, and the exit ammonia concentration were monitored. The time average ammonia concentration observed in the non-steady-state of operation was exceeded by 5-27% the ammonia concentration obtained in similar but under steady-state conditions. The enhancement in the ammonia production was mainly due to the transient state of the catalyst surface and the dynamic behavior of the reactor bed.