The molecular structure of dimethylcarbamyl chloride has been determined by gas-phase electron diffraction. The analysis, aided by a constraint from ab initio MO calculations, yielded the following bond lengths (r(g)), bond angles, and dihedral angles : C-H 1.117 +/- 0.003 Angstrom; C=O 1.202 +/- 0.003 Angstrom; (C(H-3)-N)(mean) 1.462 +/- 0.005 Angstrom; C(O)-N 1.365 +/- 0.003 Angstrom; C-Cl 1.789 +/- 0.004 Angstrom; angle N-C=O 126.5 +/- 0.2 degrees; angle N-C-Cl 113.9 +/- 0.3 degrees; angle N-C(H-3)-H 110.8 +/- 0.3 degrees; angle C-N-C(O) syn to C=O 116.0 +/- 0.4 degrees; angle C-N-C(O) syn to C-Cl 124.8 +/- 0.4 degrees; angle C(H-3)-N-C(H-3) 116.2 +/- 0.3 degrees; angle C(H-3)-N-C=O-syn 13.0 +/- 2.5 degrees; angle C(H-3)-N-C=O-anti 172.5 +/- 3.6 degrees. One of the C-H bonds attached to the O=C-N-C-syn moiety nearly eclipses the N-C(O) bond, resulting in a relatively short, 2.30 +/- 0.01 Angstrom, O ... H distance. The bond configuration around the N atom is nearly planar. Geometrical variations in a series of simple substituted amides are compared with a conventional scheme (1) of resonance structures and another scheme (2) recently proposed by Wiberg and Laidig. Scheme 2 involves charge transfer between carbon and nitrogen rather than from nitrogen to the carbonyl oxygen of Scheme 1. According to the variations of the experimentally determined geometries, the structural consequences of substitution at the nitrogen can be well interpreted by Scheme 1, while those of substitution at the carbonyl carbon, by Scheme 2.