The effects of clove oil, xylazine, cooling, carbon dioxide (CO₂), and magnesium sulfate (MgSO₄) were evaluated separately, in normal, mature crabs (n = 55) of Portunus sanguinolentus having an average weight of 69.98 ± 3.56 g (mean ± SE). In general, crabs may be anesthetized by exposure to the gaseous anesthetic agent, by immersion in a solution or by injection. Induction was stress free with clove oil and anesthesia was maintained for 100.6 ± 8.1 (mean ± SE)minutes at a ratio of 0.25 ml/lof seawater. The shortest induction time was obtained by cooling at crash ice. Thus, induction time 223.3 ± 24.77 sec and rapid recovery 100.67 ± 21.4 sec was obtained by 165 mg/l CO₂ with sea water bath immersed at 15 min. The duration of anesthesia was also longer with clove oil compared with other anesthetic agents. The objective of this study was to evaluate the effects of some selected anesthetic agents on P. sanguinolentus.