The charge transfer interactions of Azithromycin and 7,7,8,8-tetracyanoquinodimethane (TCNQ) or chloranilic acid (CL) were investigated by spectrophotometry. The apparent molar absorptivity of TCNQ complex is 2.7 x 10(4) L x mol(-1) x cm(-1) at 743 nm, and 5.0 x 10(4) L x mol(-1) x cm(-1) at 842 nm; and that of CL complex is 2.4 x 10(3) L x mol(-1) x cm(-1). Beers law is obeyed in the concentration range of 0-30 mg x L(-1) for TCNQ method, and 5-225 mg x L(-1) for CL method. The relative standard deviations of the two methods are 1.0% and 1.4% (n = 6), respectively. The composition of complex of Azithromycin with 7,7,8,8-tetracyanoquinodimethane or chloranilic acid is 1 : 2. This proposed method has been applied to the determination of Azithromycin in tablets with satisfactory results.