Crystals of bovine adenosine deaminase (ADA) grown over a two-week period in the presence of an inhibitor (ADA complex) were found to be of low quality for X-ray diffraction analysis. Furthermore, ADA incubated in the absence of an inhibitor (ADA native) did not form any crystals using conventional crystallization methods. A solution-stirring technique was used to obtain high-quality ADA complex and ADA native crystals. The crystals obtained using this technique were found to be of high quality and were shown to have high structural resolution for X-ray diffraction analyses. The results reported here indicate that the solution-stirring technique promotes nucleation and improves the quality of protein crystals.