Uspanteko (Mayan) is unique among the languages of Guatemala in having a full-fledged system of lexical tone. Tone is thoroughly integrated into the morphology of the language, and triggers several predictable phonological alternations. The Uspanteko tone system is also relatively simple, involving at most two contrastive categories. However, tone in Uspanteko shows a high degree of phonetic variability, and there is no consensus as to what tones are phonetically or phonologically active in the language. This paper argues that at least some of this unclarity owes to the effect of intonation, which can obscure lexical tone on vowels. A phonetic study attempting to control for intonation suggests that lexical tone in Uspanteko involves a privative [H]~0 contrast on short vowels, and either a [H]~0 or [H]~[L] contrast on long vowels. The relationship between the phonetics of tone and its low functional load in Uspanteko is also discussed.