Organophosphate and carbamate insecticides were used extensively for tobacco budworm control before pyrethroids became available. Resistance to them as been documented in the past but not in recent years. Since these compounds are still used in cotton it is important to continue the monitoring of the resistance levels in each of the main cotton producing areas in Mexico. Data since 1984 on tobacco budworm populations from northwestern Mexico, have showed that high levels of resistance are present to methyl parathion and methomyl. Any resistance management strategy should consider the resistance mechanisms involved in resistance to these products in order to be successful and avoid or delay cross resistance problems.