The resistance of Co–Al2O3–Si tunnel contacts for electrical spin injection from a ferromagnet into silicon is investigated. The contacts form a substantial Schottky barrier, 0.7 eV, which plays a dominant role in the electronic transport. On Si with a low doping concentration (∼1015 cm−3), the contact resistance is affected by the Al2O3 tunnel barrier only in the forward bias. In the reverse bias (the spin injection condition), the Schottky barrier results in a very high contact resistance, ∼ 102 Ω m2. While the contact resistance is improved to ∼ 10−2 Ω m2 using Si with a high doping concentration ( ∼ 5×1019 cm−3), it is still about five to six orders of magnitude higher than the value needed for resistance matching to silicon.