There is evidence that stress and focus have a magnifying lens effect on some phonetic material; however, which phonetic material is being amplified and why, and whether this material is identical in stress and focus across languages are questions for current research. Ten native speakers of Mexican Spanish produced homophonous words that differ only in stress, i.e., tonic 'dé' to give and atonic 'de' of, in three intonation contexts, namely post-focal, declarative, and focal sentences. Results indicated that duration was the strongest cue to stress; speakers consistently realized tonic 'dé' longer than atonic 'de' in declarative and post-focal contexts. This durational difference, however, was lost when atonic 'de' was placed under focus making atonic 'de' sound stressed. Thus, the magnifying lens effect of focus in Mexican Spanish does not equal that of stress because the durational differences that cue the stress contrast were lost under focus. In stress accent languages like Spanish, where stressed syllables are the most common landing site of pitch accents, focus amplifies only the phonetic material that does not interfere with the perception of the syllable as stressed.