The state-of-the-art in the evaluation of the flexural crack width development and crack control of macrocracks is described. It is based on extensive research over the past 50 years in the United States and overseas in the area of macrocracking in reinforced and prestressed concrete beams and two-way-action slabs and plates. Control of cracking has become essential to maintain the integrity and aesthetics of concrete structures. The trends are stronger than ever--toward better use of concrete strength, use of higher-strength concretes including superstrength concretes of over 20,000 psi compressive strength, use of more prestressed concretes, and increased use of limit failure theories--all requiring closer control of serviceability requirements of cracking and deflection behavior. Common expressions are discussed for the control of cracking in reinforced-concrete beams and thick one-way slabs; prestressed, pretensioned, and posttensioned flanged beams; and reinforced-concrete, two-way-action, structural floor slabs and plates. In addition, recommendations are given for the maximum tolerable flexural crack widths in concrete elements.