The experimental results of the dependence of effective segregation coefficient k(eff) of Mn(II) impurity in ammonium oxalate monohydrate single crystals during growth from aqueous solutions at a constant temperature on solution supersaturation sigma and impurity concentration and the relationship between k(eff) and face growth rates R are described and discussed. Analysis of the results revealed that: (1) the segregation of Mn(II) impurity during crystal growth from solutions is mainly associated with the time-dependent adsorption of impurities and occurs when there is a sudden increase in the growth rate, (2) the time-dependent adsorption takes place when surface coverage by the adsorbed impurity approaches a particular value, (3) k(eff) of an impurity is related with the face growth rate R of the crystals, and (4) the relationship between k(eff) and R can be described by an equation based on the model involving surface coverage due to impurity adsorption and dependence of accumulation and depletion of solvated host molecules at kinks of steps on the F faces of crystals on supersaturation. (C) 2003 Elsevier B.V. All rights reserved.