Solvent extraction of copper was carried out in a mechanically agitated vessel, using LIX-64N as the extractant. The dispersed organic phase of various drop sizes was fractionated with respect to size and subsequently each drop size interval was analyzed for its copper content using atomic absorption spectroscopy. These data, which are first such information to be reported, clearly show that the extent of copper transfer to tha organic phase strongly depends on the level of bath agitation and also on the drop size. Possible rate-controlling mechanisms were discussed in viaw of the existing theories, and a theoretical support of the experimental results was provided by performing a mass-transfer analysis.