In two experiments, the early acquisition of spatial adjectives is examined. In Experiment 1, 3- to 4-year-old and 4- to 5-year-old English children were tested for their comprehension of big, tall and long. In general, comprehension of all three adjectives improved with age, but in confirmation of Maratsos (1973) there was a sharp increase with age in one particular type of error: when asked to select the bigger of two objects, older children frequently chose the taller but smaller member of the pair. Further analysis showed that those older children who understood the word tall were especially likely to make this error. In Experiment 2, Dutch children of the same age were tested for their comprehension of groot (meaning ‘big’) and lang (meaning both ‘tall’ and ‘long’). Dutch children were also prone to choose the taller of two objects when asked to point to the bigger one, although Dutch does not possess a spatial adjective such as tall that refers exclusively to the vertical dimension. The implications of the findings for the acquisition of spatial adjectives, and for theories of semantic development are discussed.