The title compounds, 2-(dimethylamino)biphenyl-2'-carboxaldehyde, C15H15NO, and 2-(dimethylamino)biphenyl-2',6'-dicarboxaldehyde, C16H15NO2, show similar 1,6-interactions [N...C=O 2.929 (3) to 3.029 (3) Å] between the dimethylamino and aldehyde groups located in the ortho positions of the two rings, which lie at 58.1 (1)-62.4 (1)° to each other