The present study is aimed at improving the calibration of the compositional dependence of the Curie temperature (T C ) of titanomagnetite (Tmt) on the basis of temperature-dependent magnetic susceptibility (χ-T) curves measured on synthetic Tmts in the Fe-Ti-O system. In order to assess the possible influence of high-temperature cation vacancies onto the T C values, we have synthesized two types of assemblages in subsolidus conditions at 1 bar, 1100¿C and 1300¿C, under controlled oxygen fugacity conditions. Tmts synthesized in equilibrium with ilmenite-hematitess (Ilmss) are expected to have the highest vacancy concentrations, those in equilibrium with w¿stite (Wus) the lowest. The composition and homogeneity of the synthetic Tmts were carefully checked with a scanning electron microscope (SEM) and an electron microprobe (EMP). T C was determined from χ-T curves using a kappabridge and, for comparison, from M s -T curves measured with a variable field translation balance. Our data set shows systematically higher T C values for Tmt coexisting with Ilmss than for Tmt coexisting with Wus. Most χ-T curves are nonreversible, whereby the largest ΔT C (40 K) concern Tmt(+Ilmss) of intermediate compositions synthesized at 1300¿C. Nonreversibility is interpreted as reflecting cation reordering in Tmt during the high-temperature χ-T measurements. T C values obtained from M s -T curves are higher than those obtained from the χ-T curves, whereby the difference regularly increases (up to 40 K) with increasing Ti content, up to X Usp = 0.6. Our new calibration curves are suitable to retrieve Tmt compositions in basalts that were rapidly cooled and not oxidized by deuteric or hydrothermal fluids.