A lower bound, better than
those previously known, is given for the volume of a 3-dimensional body of constant
width 1. Bounds are also given in the case of n-dimensional bodies of constant width
1, n ≧ 4. Short proofs of the known sharp bounds for such bodies in the Euclidean
and Minkowskian planes are given using properties of mixed areas. An application is
made to a measure of outer symmetry of sets of constant width in 2 and 3
dimensions.