If solids are bombarded by ions, positive secondary ions (SI) of all elements of the target material are emitted. The mass analysis of these SI permits conclusions to be drawn about the composition of the target material. An arrangement based upon this kind of ion production is called an ion-bombardment ion source. In this paper it was investigated whether or not this ion source is suitable for quantitative analysis of solids by mass spectrometry. For this purpose the SI yield γ+ of 27 elements was measured at constant bombardment conditions (12 keV A+-ions, 45° incidence). γ+ is approximately 1% for 10 elements — Si, Mn, Fe, Co, Ni, Rh, Ta, W, Os, and U. Aluminium shows the largest, gold the smallest SI yield. Yields differ by a factor of 1000 for different elements. The influence of the ionization energy on the SI yield is discussed. The yield is independent of the concentration in the range 0.02—20%.