In 1965 the relation between maturity, tuber yield and under water weight was studied in 756 unselected fourth-year potato clones of twelve crosses. Other characters studied were seed potato weight, date of emergence, plant height, general impression of the tubers at lifting, tuber weight and payment weight, as the above relation could be influenced by or depend on these characters. The experiments were carried out on a clay soil at Wageningen. The experimental design was a partially balanced lattice with four replications and five plants per plot. The clone means, corrected according to F-values for blocks, were used for determinating normal correlation coefficients between all possible combinations of characters per population as well as for composition of frequency distributions and of population means with coefficients of variability. To estimate heritabilities within the populations the separate data of the four replications per clone were used. In 1966 the investigations were continued with 136 selected clones on both clay and sandy soil. In addition to the statistical operations used in 1965, normal correlation coefficients were calculated between the years and between the soil types using corrected clone means. The results are given and discussed.