Magnetic properties of dot arrays of L 11 type Co-Pt ordered alloy perpendicular films were studied. L 11 -Co-Pt films with a large uniaxial magnetic anisotropy Ku of the order of 107 erg/ cm3 were fabricated at a substrate temperature of 360 °C using ultrahigh vacuum sputter film deposition. Dot patterns with dot diameters of 70-200 nm were made using high resolution e-beam lithography and reactive ion etching (RIE). The values of Ku were measured by the GST method using the Anomalous Hall Effect; we observed the averaged signals of 6000 dots. The values of Ku for dot arrays of 10-nm-thick L 11 -Co50 Pt50 films deposited on MgO(111) substrates (single crystal films) and glass disks (polycrystalline films) were nearly the same as those of the original films independent of D, indicating no significant etching damage by the RIE process. Magnetic force microscopy images revealed that all dots were single domains in the present D region. The coercivity Hc of the dot arrays was 25.0 kOe [MgO(111) substrate, D=70 nm] and 14.3 kOe (glass disks, D=80 nm). The switching field distribution / Hc was relatively small, / Hc =0.15, even for dot arrays fabricated on glass disks, indicating the homogeneous formation of a L 11 type ordered structure in the Co50 Pt50 layers.