In order to understand the antiaromaticity of maleimides, the enthalpies of formation and sublimation of N-methylmaleimide, N-methylsuccinimide, N-methylphthalimide, and N-benzoyl-N-methylbenzamide were measured. The numerical values of enthalpies of formation for these compounds in the solid state are -329,3 ± 1.4, -469.8 ± 1.6, -325.0 ± 2.1, and -239.6 ± 3.8 kJ mol-1, respectively, while the corresponding values in the gaseous state are -256.0 ± 1.5, -389.7 ± 1.6, -233.9 ± 2.2, and -119.5 ± 3.8 kJ mol-1, respectively. The values of enthalpies of sublimation for the same compounds are 73.3 ± 0.5, 80.1 ± 0.3, 91.1 ± 0.5, and 120.1 ± 0.4 kJ mol-1, respectively. We find that the antiaromaticity of maleimides is only modest.