Present study deals with the evaluation of biosorptive removal of cadmium by red macro alga Hypnea valentiae. Experiments have been carried out to find the effect of various parameters such as initial cadmium concentration, experimental pH and temperature on the biosorption potential of H. valentiae. Optimum pH for biosorption of cadmium was found to be 6 +/- 0.3. A maximum removal of about 17 mg of cadmium per g of micro algae was observed at pH 6.0 for 250 mg L(-1) solution of cadmium. Kinetics of cadmium biosorption by H. valentiae biomass is better described by pseudo first order kinetic model. The equilibrium isotherm data are very well represented by Langmuir isotherm equation, which confirmed the monolayer coverage of cadmium onto H. valentiae biomass. Various thermodynamic parameters such as change in enthalpy, free energy and entropy were estimated. It was also clearly observed that the presence of neutral salts and other metal ions affected the cadmium uptake behavior of the biomass considerably. (C) 2009 Elsevier Ltd. All rights reserved.