We point out that inflaton decays can be a copious source of stable or long-lived particles $\chi$ with mass exceeding the reheat temperature $T_R$ but less than half the inflaton mass. Once higher order processes are included, this statement is true for any $\chi$ particle with renormalizable (gauge or Yukawa) interactions. This contribution to the $\chi$ density often exceeds the contribution from thermal $\chi$ production, leading to significantly stronger constraints on model parameters than those resulting from thermal $\chi$ production alone, particularly in models containing stable charged particles.

• Received 18 March 2002

DOI:https://doi.org/10.1103/PhysRevLett.89.091302