A slowly rotating streak camera array was used to photograph lightning flashes to two television transmission towers separated by 1.13 km. In 42 hours of thunderstorm observation the towers were struck by 36 flashes. Eighteen of the flashes occurred in pairs, with a discharge beginning on both towers within an average of about 40 ms. Duration of the two flashes in each pair overlapped, so there was always an interval during which both flashes were in progress. Tendency of the concurrent flashes to group in time, three pairs in 11 min and four pairs in about 1 hour, suggests that unique meterological conditions may have to prevail for their production. The lack of consecutive flashes separated by intervals of tens or hundreds of milliseconds is consistent with the hypothesis that the second fashes of concurrent pairs may have been tiggered by the first.