1. The chemical states of Fls produced by F19 (γ, n) reaction, with fluorobenzene, o-fluorotoluene, p-fluorotoluene and trifluorotoluene as targets, have been determined. The over-all organic retentions are 39, 33, 39 and 47 respectively. These values decrease to 20, 24, 20 and 27 when 0.2 mole fraction aniline was added prior to irradiations. The retention of solid p-fluorobenzoic acid is 15 and that of its 3 M pyridine solution is approximately zero.