Formation of negative ions via dissociative electron attachment (DEA) to the amino acid serine in the gas phase was studied using two different crossed electron/molecular beam techniques and quantum chemical calculations. Resonance electron capture mass Spectrum and effective ion yield Curves Of 16 negative ions were measured over the electron energy range from close to 0 to 11 eV. The negative ions from serine were detected from resonance states in the vicinity of 0, 1.3, 5, and 8 eV. The dominant reaction channel at low electron energies was (M - H)(-). The relative cross section for this ion exceeds more than 20 times that of any other fragment negative ions. A high-resolution experiment was applied to study fine structures in (M - H)(-) cross section. We have found that the second OH group influences some dissociative channels. Quantum chemical calculations were applied to interpret products of the DEA reaction channels.