Issue addressed: There is limited evaluation on the impact of community-based walking groups on physical activity (PA). This study examined the amount of walking and total PA minutes when adults joined the Just Walk It (JWI) program in Queensland, and changes over time. Methods: All adult participants (n=1258) were sent a survey on registration with the JWI program between April 2002 and December 2003, and after 6 and 12 months. Outcomes included self-reported minutes of walking and total PA in the past week and the proportion meeting PA recommendations. Results: Of the 1,258 registrants, 601 returned the 12-month survey; 423 of these confirmed they still participated. At baseline, 36 (8.5%) of these were inactive, 280 (66.2%) were insufficiently active to meet PA recommendations and 107 (25.3%) met PA recommendations. Among these groups, the largest 12-month increases in walking and total PA were in participants who were inactive (177 minutes, 95% CI 144-210, p<0.001 and 233 minutes, 95% CI 169-297, p<0.001, respectively) and in participants who were insufficiently active (63 minutes, 95% CI 39-86, p<0.001 and 122 minutes, 95% CI 81-162, p<0.001, respectively). Walking minutes increased more for men (n=92) [100 minutes, 95% CI 51-150] than for women (n=331) [52 minutes, 95% CI 32-72, p=0.044], as did total PA minutes (158 minutes, 95% CI 61-247 compared to 67 minutes, 95% CI 31-103, p=0.038). Furthermore, compared with participants aged 18-44 years (n=41) [-12 minutes, 95% CI -75-50] and 65 and older (n=183) [57 minutes, 95% CI 27-87], walking increased more in those aged 45-64 years (n=199) [83 minutes, 95% CI 56-110, p=0.018). Conclusions: Participation in a community-based walking group for 12 months increased both walking and total PA, especially in men, mid-aged participants and those who were inactive or insufficiently active at registration.