It is usual to characterize quantitatively a pearlitic structure by three parameters; (1) the ferrite and pearlite percentage, (2) the interlamellar spacing of the pearlite, and (3) nodule diameter of the pearlite. These parameters vary as a function of the transformation temperature. The conditions necessary for obtaining a fully pearlitic structure by continuous cooling have been determined for plain carbon steels containing from 0.2% to 0.8%C. When the carbon content is below 0.6%, pearlite is always degenerate, with low yield strength but good reduction in area. Pearlites containing more than 0.6%C always present normal cementite lamellae with high yield strength but small reduction in area. For 0.6%C steel, fragmented or continuous lamellar structures can be obtained, leading to high yield strength and reduction in area values.