Unlike Canadian English which has two liquid consonant phonemes, /ɹ, l/ (as in right and light), Japanese is said to have a single liquid phoneme whose realization varies widely both among speakers and within the speech of individuals. Although variants of the /r/ sound in Japanese have been described as flaps, laterals, and weak plosives, research that has sought to quantitatively describe this phonetic variation has not yet been carried out. The aim of this thesis is to provide such quantification based on 1,535 instances of /r/ spoken by four individuals whose near-natural, unscripted conversations had been recorded as part of a larger corpus of unscripted Japanese maintained by Dr. Nick Campbell of Advanced Telecommunications Research Institute International (ATR), Kyoto, Japan. Tokens of /r/ were extracted from 30-minute conversations between one pair of male speakers and one pair of female speakers. Each token was narrowly transcribed into the International Phonetic Alphabet, then categorized based on the author’s perception of: 1) the strength/narrowness of central oral articulatory stricture, and 2) the presence or absence of an auditory-perceptual lateral and/or rhotic sound quality. Transcription and category frequencies for each speaker averaged across all environments were then compared with frequencies in specific phonological environments to ascertain whether a particular environment was amenable to a ‘drift’ towards any particular category of variant, and whether patterns of ‘drift’ applied to all speakers or varied on an individual basis. Transcriptions of the 1,535 tokens of /r/ ranged widely among lateral and non-lateral flaps, raised (i.e. increased articulatory contact) non-lateral flaps akin to light voiced plosives (e.g. Hattori 1951, Kawakami 1977), as well as lateral approximants and rhotic approximants. While two of the four speakers, both males, patterned similarly by dividing their productions of /r/ chiefly among short lateral approximants and rhotic approximants, each speaker did vary considerably in their choice of variants in any given environment. Drift is considered in terms of physiological parameters which may be optionally exploited to maintain phonological salience.