In 1995, he ran for senator and won under the Ramos administration ticket and was re-elected to a second term in the 2001 elections, placing second among the 12 winning candidates. As senator, he authored and sponsored several landmark bills including the Traditional Medicine Law, the Social Reform and Poverty Alleviation Act, Philippine Clean Air Act, Indigenous People's Rights Act, Anti-money Laundering Act, Barangay Micro-Business Enterprise, National Service Training Program for Tertiary Students, Dangerous Drugs Act, Plant Variety Protection Act, Philippine Nursing Act, the Tobacco Regulation Act, and the law declaring Eid'l Fitr a national public holiday in the Philippines.