Most designers and builders today are familiar with the advantages of using very high density concretes for radiation shielding. Not so well known is the excellent economy which can result form the use of normal site cast concretes with locally available aggregates when space and other factors do not absolutely demand that the desired protection be achieved within minimum dimensional limits. The effectiveness of any biological shielding material is related only to its mass and concrete has an obvious advantage in this highly specialized field of construction because of its exceptionally low cost per pound. Lead is an ideal shielding material where thinness alone is a dominant consideration but it is far more expensive and has poorer structural properties than does concrete.