The objective of this work was to fit the probability density functions Normal and SB, to describe the changes, with age, in the diameter distribution of loblolly pine (Pinus taeda) stands, in the region of Caçador, Santa Catarina State, Brazil. The data came from permanent and temporary plots, with ages ranging from 5 to 11,9, grouped in age classes with intervals of 1 year. The probability density functions w...