Established suspension culture strains of Acer pseudoplatanus were analysed by chromosome counting and microdensitometric DNA measurements of individual nuclei. Comparison with the root-tip complement (2n=4x=52) showed the cultures to be entirely aneuploid with modal chromosome numbers of approximately 75 and 135 plus some cells with 250–350. Analysis of the frequency distributions of nuclear DNA values through the growth cycle of a batch culture showed that stationary phase cells accumulated in G1 of the cell cycle. Stationary phase DNA distributions could thus be used to indicate the chromosomal status of a culture without the complication of G1 and G2 DNA values for each chromosome number. Root-tip and cultured cells showed a close correlation between DNA content and chromosome number indicating that structural changes and loss of chromosomes had been at random.