The industrial relations context in U.S. automobile plants changed significantly by 1959. Union locals became more occupationally homogeneous, and the bureaucratic grievance structure functioned more effectively as a restlt. Yet, unauthorized strikes continued, albeit less frequently, and their nature was transformed. Rather than the occupationally specific xvildcats of the 1940s and 1950s, the unauthorized strikes occurring in the 1960s and 1970s were often plantwide mobilizations led by local union officials. This article explores the organizational foundations of these mobilizations. The findings suggest that striking workers in solidarity-generating labor processes were significantly more likely to choose unauthorized courses of action. The effect of the positional power of workers at the plant level was weaker, but striking workers with high levels of positional power in atomized settings were more likely to initiate unauthorized action than were those with low levels of positional power.