Using a laser monitoring observation technique, solubilities of terephthalaldehydic,p-toluic, ben zoic, terephthalic and isophthalic acids in N,N-dimethylformamide have been measured as a function of temperature in the temperature range 294.75-370.45 K. The experimental data are correlated with the lambdah equation. The calculated results show good agreement with the experimental solubilities. The molar mixing enthalpy of solution H-E is estimated from the h parameter to discuss the properties of solution. In the terephthalic acid-N,N-dimethylformamide system a repulsive interaction exists between solute and solvent, which leads to an endothermic effect during dissolution. The strongest attractive interaction exists in the p-toluic acid-N,N-dimethylformamide system, causing a significant exothermic effect.