Five commonly used developers (Acufine, Rodinal, Dektol, D19 and Microdol X) and two popular nuclear gel emulsions (Kodak NTB-2 and Ilford L4) were tested in combinations for adequacy of development characteristics and the distribution of silver particle (grain) size measured by means of a reflectance microphotometer. All developer-emulsion combinations had some range of development time during which maximum development was accomplished with no occurrence of background grains, with the exceptions of the combinations of NTB2-Acufine and NTB2-D19. Ilford L4 emulsion obtained the narrowest grain size distribution with Rodinal and Acufine, followed by Dektol, and D19. The narrowest size distribution for Kodak NTB2 emulsion was achieved with D19 followed by Acufine, Dektol and Rodinal. Microdol-X had undesirable effects on the integrity of the individual grains of both emulsions. The criteria are discussed for selecting the most advantageous emulsion-developer system for the particular mode of evaluation (visual, photometric, television camera) to be applied to the finished autoradiographic specimens.