The photofragmentation dynamics of ammonia molecules following pulsed laser excitation to the two lowest levels (vi = 0 and 1) of their A tA ; excited state has been investigated by monitoring the time-of-flight spectra ofthe nascent H-atom products. These spectra show well resolved structure. Analysis of this structure confirms recent revised estimates of the quantity DJ (H-NH2) (4.645 ± 0.01 eV) and reveals that the majority ofthe accompanying NH2 (X 2 B t ) fragments are formed vibrationally unexcited, but with high levels of rotational excitation specifically concentrated about the a-inertial axis. The detailed energy disposal is sensitive to the initially excited parent vibronic (and even rovibronic) level: the NH2 (X) fragments resulting from photodissociation via the vi = 1 level of NH3 (A) carry a higher level of excitation of the N = Ka rotational levels, which show an inverted population distribution.We also describe the results of trajectory calculations employing the recently reported [M. I. McC~rthy et al., J. Chem. Phys. 86, 6693 (1987)] ab initio potential energy surfaces for theA and X states of ammonia. These provide a detailed rationale for the experimentally observed energy disposal and highlight the massive influence on the eventual fragmentation dynamics of the conical intersection between these surfaces along the H-NH2 dissociation coordinate.