In the present work, the dynamic strain aging behaviour in microalloyed steels has been examined using a C-Mn-Al-V-N steel, which occasionally exhibits low toughness in the subcritical heat affected zone (HAZ). This may be attributed to dynamic strain aging, whereby materials show lower ductility and higher yield strength owing to the interaction between mobile dislocations and diffusing solute atoms. The research has shown that the high temperature tensile behaviour of C-Mn-Al-V-N steel depends on the presence of clusters believed to be of vanadium and carbon atoms. The interaction between dislocations and clusters of vanadium and carbon atoms at 200-450degreesC changes the work hardening rate and contributes to dynamic strain aging as confirmed in the present work. These interactions may also decrease toughness in the subcritical HAZ and lead to the subcritical embrittlement observed in the C - Mn -Al - V - N microalloyed steel.