The low-frequency field modulation technique has been employed to study the de Haas-van Alphen effect in single crystals of niobium in fields up to 10 tesla. The frequency determination of the oscillations was performed by computer-based Fourier analysis and gave five sets of frequencies, which were studied in {100} and {110} planes. Effective masses and Dingle temperatures of some orbits were measured in the symmetry directions <100>, <110> and <111>. Interpretation of the results has been based on the results of a recent augmented plane wave band structure calculation of Mattheiss (1970). Three of the observed frequency branches can be explained in terms of, and are in good agreement with, the Fermi surface predicted by this calculation. The remaining frequencies can be accounted for, if a slight distortion of the proposed model is made. Comparison of the measured effective masses with those calculated from the band structure gives a value of 2·14 ± 0·17 for the mass enhancement factor due to many body effects. Using the theory of McMillan (1968) we evaluate the superconducting isotope shift coefficient to be 0·24.