In　this　work,　the　biodegradation　of　nonylphenol　by　Rhodotorula　sp.　in　batch　culture　was　investigated　over　a　wide　concentration　range　(11　similar　to　160　mg/l).　Experimentally　nonylphenol　was　an　inhibitory　type　substrate　to　Rhodotorula　sp..　Five　kinetic　models　(Haldane,　Webb,　Yano,　Aiba,　and　Teissier)　were　fit　for　the　experimental　growth　kinetic　data.　It　was　found　that　the　Haldane　model　was　the　most　suitable　one　to　predict　the　degradation　of　nonylphenol.　The　kinetic　analysis　demonstrated　that　bacterial　growth　and　nonylphenol　degradation　of　Rhodotorula　sp.　were　based　on　a　substrate　concentration　inhibition　model.　Analysis　of　growth　factors　indicated　the　highest　specific　growth　rate　(mu)　of　0.127　h(-1)　was　obtained　at　the　initial　nonylphenol　concentration　of　12.76　mg/l.