Three alkylphenanthrenes were derived by the selenium dehydrogenation of resinic acid derivatives. 7-Isopropyl-1, 6-dimethylphenanthrene, m. p. 102∼103°(trinitrobenzene complex : m. p. 184∼185°, picrate : m. p. 169.5∼170.5°). 6-Isopropyl-1, 7-dimethyl-, oil, (trinitrobenzene complex : m. p. 188°, picrate : m. p. 178∼179°). 6-Ethyl-1, 7-dimethyl-, m. p. 70∼71°(trinitrobenzene complex : m. p. 170.5∼171.5 ; picrate : m. p. 160∼161°).