Applicability of detailed chemical kinetic models to HCCI runs in terms of ignition timings and intermediate species composition has been investigated. An existed n-heptane model and its expansion to n-decane established in this study were particularly concerned. Exhaust gas analysis showing transient composition after cool flames indicated that the unmodified n-decane model overestimates fractions of various grade of aldehydes, whereas it represents experimental ignition timings. The aldehyde yield was found to be sensitive to reactions of aldehyde with OH rather than aldehyde formation reactions. Reactions of QOOH decomposition forming HO2 were also suggested as a candidate to be revised for the model improvement on ignition delays.