This study investigates a contrast in tonal alignment that involves falling contours in Dinka. This contrast calls into question the assumption that tonal alignment cannot distinguish contour tones of the same shape within the syllable domain (e.g. Odden 1995). A qualitative description and a small-scale perception study are followed by a detailed production study. The results indicate that the main correlate of the contrast is indeed tonal alignment: the early-aligned fall sets in during the onset or early in the vowel; the late-aligned fall sets in well into the vowel. The production study also suggests that it is unlikely for more than two patterns of alignment in contour tones of the same shape to be accurately produced and perceived, given various phonetic limitations. The contrast is represented phonologically using a binary feature. This representation is adequate in an explanatory sense, in that the category boundary is in line with the quantal threshold hypothesized in House 1990. The results also corroborate the hypothesis of three-level vowel length in Dinka.