This article assesses tonal oral reading errors in the 1982 orthography of Eastern Dan, a South Mande language of Côte d'Ivoire. Fifty-seven adult participants orally read four narrative texts presented with and without tone marks. Subsequent linguistic analysis of tonal errors identified six possible causes: dialect diversity, homophony, tonal minimal pairs, alternating visually similar words, under-representation of longer words, and misspelled words. Extending the analysis to errors on individual tones reveals that the orthographic strategies for marking mid, low, extra-low and contour tones do not attract more tonal errors than any other tone. The paper concludes by acknowledging that many tonal errors are apparently not linguistically motivated at all and are probably due to lack of regular reading practice given the current stagnation in the literacy program.