We assess evolution in performance, efficiency and productivity of Colombia's power distribution utilities before and after the 1994 regulatory reform that introduced electricity market activities for the power sector in 12 distribution companies from 1985 to 2001. Performance is evaluated contrasting changes in mean and median by Wilcoxon Rank Sum and Pearson test on financial and other performance indicators. Technical efficiency is measured by means of Data Envelopment Analysis (DEA). The nature of the dataset allows the estimation of Malmquist productivity index and its evolution in time. Results show a recovery after therefrom in the mains performance indicators of profitability, partial input productivity, and output. Plant efficiency and productivity increased after de reform, mainly in the largest utilities used as benchmarks in the DEA efficiency scores measures. Meanwhile, the less efficient power distribution companies did not improve after the reform and were not able to undertake plant restructuring to catch up in plant efficiency with respect to the Pareto efficient input allocation. Econometric results on DEA efficiency scores suggest a positive effect of policy reform.