An optimal pesticide tax would discriminate among the substances marketed according to their toxicity levels. Adopting such a tax in Mexico is the most efficient way to prepare for compliance with the future extension of the list of pesticides subject to phase-outs and elimination under international agreements. This article examines the implications of three different environmental tax options: a general 15% tax on all pesticides (compensating for their current exemption from the value-added tax), a differential tax of 15, 10, 5 or 0% based on toxicity levels; and a 10% tax focused on the most toxic substances currently authorized. Tax revenues should be used to restore human and ecosystem health and compensate for other types of damage as appropriate.