This paper addresses the impact of class position on collective action by comparing workers' and business' associational organizability. Hypotheses on this are derived from class theory, collective action theory and organization theory. When examining them via a crossnational comparison of labor unions and business interest associations, class-specific differences arise: a higher organizability accrues to business interest associations in terms of the ability to recruit members, but to unions in terms of internalizing interests and making members comply. No theory's hypotheses are completely consistent with these findings. Their shortcomings are discussed, and a revised theoretical approach is developed. The paper's final section discusses some consequences of the observed differences for business' and unions' interest policies.