Sanctions are a crucial part of enforcing environmental regulations. We discuss the determinants and the levels of monetary penalties for environmental offenses found in practice. Three major categories of variables are distinguished: the circumstances of the offense, the characteristics of the offenders, and the indirect political and institutional effects. Some general trends emerge: fines increase with the harm caused by the offense and fines are higher for repeat offenders as well as for intentional offenses. Also, the studies discussed indicate that political and institutional factors matter. The empirical studies provide some initial insights into the objective functions of courts and agencies.