High functioning children with a diagnosis of autism or Asperger's syndrome (HF-ASD) often experience difficulties organising goal-directed actions in their day-to-day lives, requiring support to schedule daily activities. This study aimed to capture these everyday difficulties experimentally using multitasking, a methodology that taps into the cognitive processes necessary for successful goal-directed activities in everyday life. We investigated multitasking in children with HF-ASD using a novel multitask test, the Battersea Multitask Paradigm. Thirty boys participated in the study,-14 with HF-ASD and 16 typically developing controls, matched for age and IQ. Group differences in multitasking were observed. Participants with HF-ASD were less efficient at planning, attempted fewer tasks, switched inflexibly between tasks and broke performance rules more frequently than controls.