Clinopyroxenes from pyroxenite, ijolite and nepheline syenite from the main intrusion of the Alnö complex define two sub-parallel compositional trends with respect to Na, Ca and Fe TOT plotted against alkali-pyroxene fractionation index (Na–Mg). Both trends define a smooth fractionation of increasing Na and Fe TOT and decreasing Ca with increasing Na–Mg, but one set of samples contain clinopyroxenes that constantly plot at higher Na and lower Fe TOT and Ca (at similar Na–Mg) than the rest of the samples. Clinopyroxenes with higher Ca and Fe TOT and lower Na (trend 1) co-exist with substantial amounts of Ti-andradite (up to 70 vol.%), while the sample set defining the more Na-rich trend (trend 2) lack co-existing Ti-andradite. Clinopyroxenes from both trends show fractionated REE patterns with a distinct difference in HREE content, reflecting the content of co-existing Ti-andradite. The rocks of the first Ti-andradite-bearing trend crystallized slightly prior to the rocks of the second trend, probably from a primitive, Ca- and Ti-rich nephelinitic magma. Crystallisation of pyroxenite and melteigite occurred under low aSiO 2 and high aCaO and aTiO 2 as evidenced by the presence of perovskite and sometimes substantial amounts of magnetite. Subsequent increase in aSiO 2 is evidenced in the overgrowth of perovskite by titanite, which in turn is overgrown by Ti-andradite. Nepheline syenitic residuals crystallized under higher aSiO 2 and aNa 2 O and lower aCaO and aTiO 2 , which reduced Ti-andradite into an accessory phase and produced more Si- and Na-rich clinopyroxenes. Some of these residuals probably also mixed with new primitive magma producing a hybrid magma that crystallised the more Na-rich and Ca- and Fe TOT -poor clinopyroxenes of trend 2. The complete lack of Ti-andradite in these rocks indicates different crystallisation conditions and also a different magma composition.