The chromosome numbers and frequency of polyploids were compared in life forms of Asteraceae, Poaceae and Rosaceae. Both parameters were higher in Poaceae and Rosaceae than in Asteraceae. Among the life forms, longlived plants including perennials and woody plants (shrubs and trees) generally had higher chromosome numbers and consequently polyploid frequencies than short-lived species (annuals and biennials). The families surveyed have different frequencies of life forms. Asteraceae and Rosaceae are both dicots, but the life forms in Asteraceae are more similar to Poaceae than to Rosaceae. To separate the influence of life form, in a series of tests we compared life forms from the same families. These results also showed that long-lived forms generally have more chromosomes than short-lived ones.K Ke ey y w wo or rd ds s: : Chromosome numbers, polyploidy, life forms, plants, evolution, Asteraceae, Rosaceae, Poaceae, threshold method, x method.