In this study, the kinetics of disappearance of radioactivity in aerobic composting was investigated. For this put-pose, compost materials were prepared by mixing sugar beet wastes, wine factory wastes (grape wastes), straw and biological treatment sludge in different amounts. While alpha-radioactivity was not initially detected in all composting materials, the composting materials had some beta-radioactivity. In the mixtures of sugar beet wastes -straw-biological treatment sludge (1), sugar beet wastes-wine factory wastes (grape wastes)-biological treatment sludge (II) and wine factory wastes (grape wastes)-biological treatment sludge (III), the beta-radioactivity reduced by 82%, 58%, 85% respectively of initial values after 52 d. The beta-radioactivity degradation in the composting process could be represented by first-order kinetics and reaction rate constants of mixtures of I, II and III were k = 0.0693 d (1) (R-2 = 0.84), k = 0.0453 d(-1) (R-2 = 0.98), k = 0.0234 d(-1) (R-2 = 0.97), respectively.