Eleven chalcones were prepared and tested as antinociceptive agents using the writhing test in mice. Some compounds, given intraperitoneally, caused potent and dose-related antinociception, being several times more active than some reference drugs. The results evidenced that some physico-chemical parameters are involved in the pharmacological activity. 3,4-Dichlorochalcone (2) was the most effective compound, and was also studied in another model of pain in mice, the formalin test. Here it inhibited only the inflammatory pain (second phase), being equipotent to the reference drugs.