This invention provides an improvement to methods of drug loading of ultrasound contrast agents. Echogenic drug-loaded polymer microcapsules, nanocapsules, or mixtures thereof produced by the method of the invention wherein the echogenic drug-loaded polymer microcapsules, nanocapsules, or mixtures thereof contain at least 10% more of a drug as compared to (1) echogenic drug-loaded polymer microcapsules, nanocapsules, or mixtures thereof prepared by adding drug prior to emulsifying or (2) echogenic drug-loaded polymer microcapsules, nanocapsules, or mixtures thereof prepared by adding drug to lyophilized polymer microcapsules, nanocapsules, or mixtures thereof.