Previous research shows that English-learning 7.5-month-olds are biased to segment speech at strong syllables consistent with the predominant trochaic (strong-weak) pattern of words in their language (Jusczyk, Houston, & Newsome, 1999). The present study asked whether 7.5-month-olds can use a familiar name to override their metrical bias and segment iambic (weak-strong) words from natural speech. Infants were familiarized to passages containing weak-strong-weak sequences ("guiTAR is") preceded by "Mama/Mommy" or an unfamiliar name. Infants were tested on iambic words ("guiTAR" in Experiments 1-2) or trochaic nonwords ("TARis" in Experiment 3). Segmentation occurred only for iambic words that were preceded by "Mama/Mommy" during familiarization. The presence of "Mama/Mommy" attenuated infants' bias to treat strong-syllables as word onsets. We suggest that young infants weight highly familiar words more strongly than metrical information and discuss the implications of this finding for a hierarchical model of segmentation that connects infant and adult segmentation systems.