This article attempts to analyze the causes of the irregular readings of Chinese characters both in Mandarin and in Sino-Korean (i.e. Korean pronunciations of Chinese characters). Cultural taboo, avoidance of confusion and residues of historical and/ or regional sound changes are the main causes for irregular readings in Mandarin. Semantic readings, euphony, mismatched palatalization, confusion and erroneous readings are the main reasons in Sino-Korean, among many others. This article also examines how well the graph of a Chinese character conveys the sound if it is a phonetic compound, which consists of a phonetic element and a semantic element. The discussion highlights that the function of conveying the exact pronunciation of a Chinese character is not straightforward although DeFrancis (1984b: 19) suggests that “Chinese is basically a phonetic system of writing of the syllabic type.”