Electron-impact excitation of vibrational motion of molecules is reviewed, particularly for polyatomic molecules. A polyatomic molecule has multiple modes of vibration. The excitation cross sections for different modes show different behaviour as a function of collision energy. After a brief introduction of theoretical methods, the mode dependence is discussed from two points of view: infrared activity and resonant excitation. Experimental data on the vibrational cross section are available for many polyatomic molecules. The availability of those data is summarized for future applications. For an infrared active mode of vibration, a simple theoretical method using the Born approximation is often applied to an analysis of experimental data or an estimate of the cross section. The applicability of the Born formula is discussed in detail.