In scintillation/photomultiplier timing systems, jitter is influenced by the generation rate of photons in the scintillator, variations in the photon transit times through the scintillator, the transit time variations of photo electrons from the photocathode to the first dynode, statistical fluctuations in the gains of the individual dynodes, and, to a much smaller degree, the width of the single-electron response of the PMT. Normally, the signal amplitude at the anode output is large enough to make the input noise of the succeeding electronics a negligible contributor. Best time resolutions are obtained from scintillators with small mechanical size, efficient light collection, high light output, and short fluorescence decay times. The photomultiplier should be chosen for high photocathode yield, small photocathode diameter, high first-dynode yield, minimal transit-time spread, and a reasonably narrow single-electron response. With a 14-stage PMT the anode output pulse is usually large enough to be connected directly to the input of the timing discriminator. Eight- or ten-stage PMTs may require some amplification, as described in the introduction to Preamplifiers and Amplifiers.