The condition is derived for Friedman 's trigger strategy to sustaina collusive market equilibrium as a noncooperative Nash equilibriumgiven subjective beliefs as to the antitrust authority's ability of suc-cesfully dissolving the illegal cartel.

The Routh-Hurwitz stability condition is disentangled for choice variables that are strategic substitutes or strategic complements. This yields distinct stability conditions that are not necessarily symmetric. Two examples illustrate this result.