The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound [yields] bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN[sup [minus]], NCO[sup [minus]] and NCS[sup [minus]]. Transition state photoelectron spectra are presented for the following systems Br + HI, Cl + HI, F + HI, F + CH[sub 3]0H, F + C[sub 2]H[sub 5]OH, F + OH and F + H[sub 2]. A time dependent framework for the simulation and interpretation of the bound [yields] free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH [yields] O([sup 3]P, [sup 1]D) + HF and F + H[sub 2]. The theoretical approach for the simulations is a fully quantum-mechanical wave packet propagation on a collinear model reaction potential surface. The connection between the wavepacket time evolution and the photoelectron spectrum is given by the time autocorrelation function. For the benchmark F + H[sub 2] system, comparisons with three-dimensional quantum calculations are made.