The aim of this study was twofold. First, it evaluated the developmental changes on frequency of use, efficiency, and choice of counting strategies from childhood to adulthood. Second, it determined the adaptation of the counting strategies to the structural features of the task. Participants in seven age groups ranging from 5-year-old to adulthood were asked to count dots in arrays varying on size, arrangement, density and size of the subgroups. The nature of the strategies used and their efficiency, i.e. speed, accuracy and rate of manual pointing, were recorded using the overt behavior technique. The developmental pattern of results for the four main strategies, counting by ones, by ns, addition and multiplication, was in line with Siegler's overlapping waves model. The structural features affected the use of the strategies since 13 years, except for the multiplication strategy. Finally, intra- and inter-individual variability in strategy showed a monotonous increase with age. Implications for understanding the development of counting skill are discussed. (Contains 2 tables and 2 figures.)