The previously reported resistance of 9-substituted adenines to ring alkylation in alkaline medium was profited from to prepare all 7 possible O''methyl derivatives of the [cancer] therapeutically important 9-.beta.-D-arabinofuranosyladenine (araA) by mild methylation of the latter with dimethylsulfate in aqueous alkaline medium. All products were fractionated and isolated in a single step on a Dowex OH- column. The sequence of elution of the various derivatives was strikingly similar to that for the O''methyl derivatives of 1-.beta.-D-arabinofuranosylcytosine, previously reported, suggestive of a similar sequence of acidities of the sugar hydroxyls. The products were identified by various criteria, including PMR spectroscopy, extensive data for which are supplied. The 2''-O-methyl and 3''-O-methyl derivatives of araA exhibited appreciably lower susceptibility to calf intestinal adenosine deaminase than the parent araA. The 5''-O-methyl analogue was fully resistant to enzymatic deamination.