Characteristic volatile components of roasted semi-dried horse mackerel were investigated by comparison with the following samples: （1） roasted semi-dried yellow sea bream and sardine, （2） three roasted fishes, （3） three boiled fishes, （4） three semi-dried fishes and （5） three raw fishes. The Maillard reaction and the lipid oxidation were then studied to elucidate the production mechanisms of the characteristic volatiles by roasting.
2-Methylpropanal, 2-methylbutanal and 3-methylbutanal were identified as the main characteristic components of three roasted semi-dried fishes by gas chromatography and gas chromatography-mass spectrometry, and the peak areas of these components were larger than those of the three roasted fishes. These components were found to be produced by the Maillard reaction during heating and to contribute to the roasting odor partially.
On the other hand, propanal and 2-ethylfuran, which were identified in the roasted sun-dried horse mackerel and the semi-dried sardine, were thought to be produced by lipid oxidation.
Moreover, 2-methylpropanal and 3-methylbutanal were increased by adding valine and leucine, and masked the rancid odor.