Photoluminescence (PL) efficiency of CdTe nanocrystals was investigated as a function of the ratio of surfactant (thioglycolic acid, TGA) to Cd2+ used in aqueous preparation. When the ratio was 1.3, a maximum PL efficiency of 65% was obtained. Within our knowledge, this value is the highest ever reported for as-prepared aqueous solution. Surfactants added more than the optimal amount tend to gather densely on the nanocrystals, and distort the surface. This might be one explanation of the decrease of efficiency.