10-Methyl-10-benz [b] fluorenylmethyl tosylate gave mainly 5-methylbenz [a] anthracene on formolysis, but the related alcohol gave a mixture of the 5-and 6-methyl isomers by reaction with phosphorus pentoxide. Reaction of benz [b] fluorenone with excess diazomethane gave 5-methoxybenz [a] anthracene as the only isolable product. The alkylation of methyl benz [b] fluorene-10-carboxylate was studied.