Analyzing Dutch criminal cases of adultery in the eighteenth and nineteenth centuries, this article shows that the legal definition of adultery as well as its prosecution changed in this period. Until 1811 both men and women received equally hard punishments and were prosecuted in similar numbers. Only with the introduction of the French Code Pénal in the Netherlands in 1811 did the double standard find its way into laws on adultery. But at the same time, sentences became more lenient and prosecution declined. The changes in the laws, as well as the discrepancies between the law and prosecution practice, show adultery's constructed character and its differing meanings, the variability of the double standard and the precarious nature of heterosexuality.