Pyroxene equilibration experiments were carried out in a multivariate system at 10--15 kbar pressure and 925¿--1150 ¿C using PbO flux. Two starting mixes were used: one is a natural spinal lherzolite and the other is a 50:50 molar mix of synthetic diopside and enstatite crystals. Large (50--100 μm), homogeneous, euhedral crystals of pyroxenes were grown in the presence of a lead silicate melt in the interface region between the two starting mixes. These pyroxenes gave partitioning coefficients for En and Di exchange reactions that are slightly different from those obtained from CaO-MgO-SiO2 and CaO-MgO-Al2O3-SiO2 systems. Two new practical thermometric equations were derived which gave similar temperatures as those obtained with the Bertrand and Mercier (1986) thermometer. All other temperatures gave higher values. The Mercier et al. (1984) spinal peridotite barometers reproduced the run pressures quite well but were unable to give reasonable pressure estimates for natural spinel peridotites from Hawaii. Fs component of clinopyroxene showed an apparent P dependence which needs to be verified with studies of simple systems containing iron. ¿ American Geophysical Union 1989