The valence electron density of the NH 3-BF 3 complex has been calculated in the iterative extended Hückel approach, and the results are presented in the form of contour diagrams of the charge distribution of the complex as well as its constituent molecules. In this approach the complex is formed under a transfer of 0.76 electrons from ammonia to boron trifluoride. This is commented on particularly on the basis of contour diagrams of the density difference between the complex and constituent molecules. The corresponding charge transfer obtained by the CNDO/2 method is 0.43 electrons.