The adsorption of 4-picoline (4-methylpyridine) on the Cu(1 10) surface has been studied with time-of-flight electron stimulated desorption ion angular distribution (TOF-ESDIAD) and other methods. Using deuterium labeling in the methyl group and hydrogen labeling on the aromatic ring, it has been possible to separately monitor by TOF-ESDIAD the C-D bond directions and the C-H bond directions in the adsorbed molecule. These triangulation measurements have led to a detailed understanding of the conformation of the adsorbed molecule relative to the Cu(1 10) crystal lattice, allowing one to witness changes in the molecular conformation as adsorbate-adsorbate interactional effects take place for increasing coverages. At low coverages, the molecule adsorbs by the N atom at an atop Cu site with the aromatic ring parallel to the <001> azimuth and with the molecular axis inclined 33 (+/-5)degrees along the <001> azimuth. As rows of 4-picoline molecules form long range ordered chain structures oriented along the <112> azimuth, the aromatic ring twists 29degrees about the inclined molecular axis as a result of forces between the adsorbate molecules. The initial tilting of the molecular axis at low coverage is likely due to the interaction of the positive-outward dipole with its image in the substrate. The ring twist may result from dipole-dipole forces between the adsorbate molecules in the rows formed tending to form nested parallel pyridine rings. These studies are the first to apply the TOF-ESDIAD method for the measurement of the direction of chemical bonds at more than one molecular location within an adsorbed molecule and the new method is named electron stimulated desorption-molecular triangulation (ESD-MT). The results obtained give information of importance in understanding the factors which control conformational effects during the molecular self-assembly of complex adsorbed molecules on surfaces.