The present study investigated the perception and production of English /w/ and /v/ by native speakers of Sinhala, German, and Dutch, with the aim of examining how their native language phonetic processing affected the acquisition of these phonemes. Subjects performed a battery of tests that assessed their identification accuracy for natural recordings, their degree of spoken accent, their relative use of place and manner cues, the assimilation of these phonemes into native-language categories, and their perceptual maps (i.e., multidimensional scaling solutions) for these phonemes. Most Sinhala speakers had near-chance identification accuracy, Germans ranged from chance to 100% correct, and Dutch speakers had uniformly high accuracy. The results suggest that these learning differences were caused more by perceptual interference than by category assimilation; Sinhala and German speakers both have a single native-language phoneme that is similar to English /w/ and /v/, but the auditory sensitivities of Sinhala speakers make it harder for them to discern the acoustic cues that are critical to /w/-/v/ categorization.