Ancestor worship is a dilemma for Christian communities in Korea and Africa, who have difficulty adapting Western theology to their Third World cultures. Allan Culpepper calls ancestor worship a cultural phenomenon, not a hindrance to the Gospel message, which this article refutes. Ancestor worship is religious rather than social in function. Common features of ancestor worship in Africa and Korea are 1) conventional superstition (shamanism in Korea, animism in Africa), 2) belief in immortality, and 3) ancestor veneration / filial piety. Theological assessment reveals the incompatibility of ancestor worship with Christianity. 1) Fear of ancestors is replaced by liberation in Christ. 2) The dead exist in a mode completely different to earthly existence and have no power in the world. 3) Ancestors cannot fulfil the intermediary role reserved for the Holy Spirit. Ancestor worship should be viewed as idol worship. Contextualisation of kerygma becomes distorted when religious pluralism is tolerated.