A blood chemistry profile on grouper was developed by establishing baseline ranges forseveral clinical chemistry tests (including red and white blood cell counts, GOT, GPT,glucose, total protein, albumin, lactic acid, and the serum ion of Na, K, Ca).Meanwhile, the relationship among the hematology and serum chemistry and thepathogens were compared for diseases prevention and control.The in vitro activity of sulfonamides was assessed by determination of minimuminhibitory concentration and zone diameter breakpoints using the methodology andcriteria recommended by the National Committee for Clinical Laboratory Standards(NCCLS) and British Society for Antimicrobial Chemotherapy (BSAC). The efficacy oftreatments of sulfonamides in vivo after experimental infection of fish was also evaluated.