Isocoumarin content changed little in peel or pulp of control carrots during the post-treatment period. Treatment with MCP alone did not affect isocoumarin accumulation. Eth-ylene treatment stimulated isocoumarin accu-mulation, with the content in the peel increas-ing continuously during the 16-d posttreat-ment period at 10 °C and pulp contents reach-ing a maximum 12 d after treatment. After 16 d exposure to ethylene, isocoumarin content was 39 times as high as control in both peel and pulp, although the peel contained seven times more isocoumarin than the pulp. Treatment with MCP before exposure to ethylene totally eliminated the effect of ethylene onisocoumarin accumulation.