The well-documented evidence that bilinguals demonstrate cognitive advantages over monolinguals is used as a foundation for the hypothesis that bilinguals will be better able to solve certain spatial tasks, and a theoretical framework for this hypothesis is constructed. The paper describes an experiment to explore this hypothesis. A series of spatial test items involving the comparison of diagrams of like and unlike pairs of knotted and unknotted ropes at varying orientations was given to 41 subjects. The subjects were 11 balanced bilingual Welsh/English and 30 monolingual English speakers. Bilinguals performed the tasks more quickly than monolinguals. The tasks were intended to stimulate the use of mental imagery in their execution. There was a difference in complexity across the 72 test items and some of the tasks were processed more slowly than others by all subjects. For example, rotation of one of the pair increased the processing time for both monolinguals and bilinguals. The results indicate that, as well as showing greater proficiency overall, bilinguals were better able to deal with the more complex tasks. The findings are taken to show a relationship between some aspects of spatial ability, mental imagery and bilingual language processing. (Contains 3 figures, 4 tables, and 1 note.)