The reduction of CuBr2 by NaBH4 in a variety of solvents yields nanoscale metallic copper as the primary product. Although the product of this reaction is largely solvent independent, the studies show that reaction times, the total volume of gaseous products, and nanoscale particle sizes are dependent on solvent properties. The reaction occurred instantaneously in polar, protic, and acidic solvents such as methanol and ethanol. In contrast, in polar, aprotic, and coordinating solvents such as tetrahydrofuran and acetonitrile, the reaction was slow. Particle sizes increased as the rate of reaction decreased. For solvents in which similar reaction times were observed, the reaction carried out in polar, aprotic, and coordinating solvents yielded copper samples with larger particle sizes. The acid propel-ties of the solvent controlled the amount of gas evolved in these experiments.