The present experiments investigated the flexibility of statistical word segmentation. There is ample evidence that infants can use statistical cues (e.g., syllable transitional probabilities) to segment fluent speech. However, it is unclear how effectively infants track these patterns in unfamiliar phonological systems. We examined whether English-learning 14-month-olds could segment continuous speech in an artificial language consisting of Mandarin Chinese syllables. Syllable transitional probabilities provided the only reliable word boundary cues. In Experiment 1, we found that males segmented the language; they reliably discriminated words from the language versus across-word sequences. Females did not display reliable discrimination. In Experiment 2, when the test items were designed to have less overlap in their statistical structure, males and females displayed successful learning. Variation in direction of preference was revealing about infants' processing in the tasks. Taken together, the findings indicate that infants' statistical word segmentation abilities are sufficiently robust for processing speech streams containing foreign sounds.