The spin-forbidden channel, NH(X (3) Sigma(-))+CO, has been observed directly in the photodissociation of jet-cooled HNCO following S-1<--S-0 excitation. The NH(X (3) Sigma(-)) yield spectrum is obtained in the energy regimes near the thresholds to H+NCO and NH(a (1) Delta)+CO channels. The spectrum is similar to the NCO yield spectrum when direct dissociation on S-1 is not significant. At photolysis energies >43 400 cm(-1), state specific differences between the NH(X (3) Sigma(-)), NH(a (1) Delta) and NCO yield spectra are observed, and at energies >44 000 cm(-1) all structure in the NH(X (3) Sigma(-)) yield spectrum is lost, while the NH(a (1) Delta) yield spectrum remains structured. The results are interpreted in terms of the different time scales for intersystem crossing and dissociation.