The DHVA effect in single crystals of TiBe2 has been investigated in magnetic fields between 10 and 35 T using a pulsed-field system. Two sheets of Fermi surface are found, an electron sheet around Gamma and an X-centred hole sheet. Both are split into a majority-spin ( to ) and a minority-spin ( down arrow ) surface. In the field region studied Delta F=Fto -Fdown arrow amounts to about 200 T or 10% of the average frequency values. With the field direction parallel to (110) the field dependence of the splitting of the Gamma orbit is studied in detail. It is found that the difference in spin-up and spin-down Fermi surface areas is directly proportional to the magnetisation, within the experimental error. This is in agreement with the Stoner model. Departures from this model due to spin fluctuations are expected below 10 T. The effective masses of the Gamma and X orbits show large enhancements of about lambda =3 and 1.5 respectively.