Ammonia-c13 of differing l4N/l5N ratios has been photolysed in the 2-8 transition using a narrow-band-width, frequency-doubled, pulsed dye laser. At specific excitation wavelengths, chosen by absorption spectroscopy, the product nitrogen is enriched in I5N, a maximum enrichment factor of 4.8 being attained. The initial isotopic selectivity of excitation is largely retained in the nitrogen product, even though the primary photodissociation forms free radicals and N, is formed only after a sequence of secondary reactions. Quantum yields of nitrogen and hydrogen formation have been measured at very low conversions as a function of the time of irradiation. The initial yield of nitrogen appears to be zero and that of hydrogen 0.25.