Four acid dyes were adsorbed on lignite (porosity 0.6335) from aq. solns. at initial concns. 1-1000 mg/L under static conditions. The lignite was an efficient sorbent (capacity 3.8-22.7 g/kg). The process was successfully described by Langmuir, Freundlich and Dubinin-Radushkevich isotherm equations.