Relative differential cross sections are presented for elastic scattering of electrons by sodium, potassium and rubidium atoms in the energy range from 150 to 500 eV. The data were obtained at angular intervals of 10 degrees from 30 degrees to 120 degrees . The cross section curves show a minimum around 100 degrees for sodium and potassium and 80 degrees for rubidium, the depth of the minimum decreasing with increasing energy. A comparison with previous experimental data and various theoretical models indicates the dominance of static and absorption potentials in the elastic scattering channel and the weak binding of valence electrons in the alkali atoms.