LiMnPO4 was synthesized using a sol–gel method and tested as a cathode material for lithium ion batteries. After calcination at temperatures between 520 and 600 ◦C, primary particle sizes in the range of 140–220 nm were achieved. Subsequent dry ball milling reduced the primary particle diameters from 130 to 90 nm, depending on time of ball milling. Reversible capacities of 156 mAh g−1 at C/100 and 134 mAh g−1 at C/10 were measured. At 92% and 79% of the theoretical values, respectively, these are the highest values reported to date for this material. At faster charging rates, the electrochemical performance was found to be improved when smaller LiMnPO4 particles were used.