This indicator is used to estimate the effect on bid rigging of stepped up enforcement activity by the U.S. Department of Justice antitrust unit in southern States in 1980-1982. When enforcement measures are combined into a loss formulation, in all cases, an increase in expected costs of rigging a bid due to antitrust liability reduced the amount of rigging actually going on in the highway construction industry. Surprisingly, with severity of punishment controlled, certainty of punishment did not appear to affect rigging or markups. This suggests that increased penalties, rather than increased enforcement activity, were more effective in controlling bid rigging. Supplemental data are appended. 3 figures, 10 tables, 28 footnotes, and 10 references.