X-ray diffraction, physical density, and magnetization measurements have been performed on a series of electrodeposited amorphous Co-P alloys between 19.0 and 23.6 at. % P. Although the radial distribution function of the 22.0 at. % P alloy exhibits characteristic features of a Bernal dense random packing of equal size hard spheres, more detailed comparisons indicate that binary random packing, with smaller spheres representing P atoms, would be a more appropriate structural model. For this alloy the nearest neighbour distance (dominated by Co-Co pairs) is 2.58 ± 0.5 Å and the average first coordination number is 13.0 ± 0.5. Low and high field magnetization measurements from 5 to 700 K indicate that the alloys are ferromagnetic with low temperature demagnetization following a T3/2 temperature dependence almost to Tc/4, that the Curie temperatures Tc are between 550 and 750 K, and that nB, the magnetic moment per Co atom at 0 K, varies from 1.15 to 1.36 Bohr magnetons. Both Tc and nB decrease with increasing P content