Competitive adsorption-desorption kinetics of arsenate [As(V)] and phosphate (P) was investigated in soils having mixed As(V) and P solutions at different concentration ratios. Three soils having different properties were used and sampling at different reaction times of sorption was followed by successive dilutions to measure the rate of release during desorption. For all soils, As(V) and P adsorption was highly time-dependent, with decreased sorption rate with increasing reaction time. Rates and amounts of As(V) adsorption were significantly reduced with increasing P concentration. Moreover, As(V) and P exhibited different sorption affinities among the different soils, suggesting that specific sorption perhaps play a significant role in their interactions. Result from miscible displacement experiments into uniformly packed soil columns demonstrated that the introduction of phosphate substantially reduced the amount of As(V) retained by soil column and the increase of arsenic release or mobility.