A new skeletal mechanism of toluene reference fuels with nitric oxide (TRF-NO) in homogeneous charge compression ignition (HCCI) combustion is presented to investigate the effects of NO in exhaust gas recirculation (EGR) on combustion. The skeletal mechanism of TRF-NO, consisting of 80 species and 184 reactions, works in combination with the mechanisms of toluene and primary reference fuel (PRF). The toluene sub-mechanism is developed by simplifying detailed or semi-detailed mechanisms based on reaction paths and sensitivity analysis. Cross reactions are considered to show the interactions of the three TRF components when combined. The reaction paths of NO are summarized by analysis of the detailed NO mechanism to reflect the effects of NO on TRF. Combining reaction paths with sensitivity analysis at different conditions, the simplified NO sub-mechanism is proposed. Then, the final TRF-NO skeletal mechanism is formed by combining the NO sub-mechanism with the TRF mechanism. The new skeletal mechanism is validated by comparison of the experimental data in both a shock tube and an HCCI engine over a large range of temperatures, pressures, and equivalence ratios with single-fuel component and their blends of TRF. Furthermore, validations of the new skeletal mechanism also include the effects of NO on ignition delay times with different compositions, proportions of three TRF components, and under different operation conditions. (C) 2015 Elsevier Ltd. All rights reserved.