In this paper, two conceptually different statistical distance metr i c ~ are defined and analyzed. First, the asymmetric acoustic distance measures how the acoustic property of one phoneme is close to that of another, and is defined here based on the Mahalanobis distance between two hidden Markov models. Second, the asymmetric phonemic distance, measures how probable a phoneme is realized as another, based on the aligned phonemic canonical and surface transcriptions of speech corpora. These two mutually dependent distance measures are used to construct an abstract acousridphonemic disrance plane which is helpful in quantitatively analyzing pronunciation vatiations. Besides, clear distinction and complicated correlation between these two distances were discussed, which is believed to he helpful in many application areas involving lexical design and acoustic modelling as well. Preliminary analysis were performed on LDC Hub-4NE Mandarin Broadcast News database. and possible application in pronunciation modelling was discussed.