Relationship between the rotation period of large asteroids and their oblateness (c∕a ratio). We observe a linear relation between both physical properties with a correlation coefficient of r = 0.48 (N = 42), a 99.8% confidence level that this correlation is not random. All multiple systems observed within our programme possess a rotation period of below 6h and a c∕a axis ratio of below 0.65 except (31) Euphrosyne).