The radicals generated from saturated fatty acids and their derivatives by hydrogen abstraction with photochemically formed t-butoxyi radicals have been investigated. These arise from the various methylene groups in the acids. The relative rates of abstraction from the methylene groups in the α-position, the position adjacent to the terminal methyl, and the remaining chain positions are 2:2:1, respectively, at 290 K, for acids of chain length >C₆. With propanoic acid, butanoic acid, and butanonitrile, hydrogen abstraction at the α-methylene group predominates. With 1-lauroyl-2-myristoyl-3- palmitoyl-rac-glycerol, enhanced attack at the position adjacent to the terminal methyl was observed.