An author error occurred in this paper by Carolyn DiGuiseppi and colleagues (8 March, pp 710-3). The fourth and fifth sentences in the third paragraph of the results should have read: “Girls showed substantially larger declines in walking (23% [not 30%]) and cycling (39% [not 64%]) and smaller increases in car travel (35%) than did boys (15%, 23%, [not 18%, 30%] and 45% respectively). Children aged 10-14 showed the largest decline in walking (26% [not 35%]) compared with children aged 0-4 (9% [not 10%] and 5-9 (17% [not 20%].” These changes do not alter the meaning of the two sentences or affect any of the subsequent discussion.