The explosive development of protein and peptide drugs has ushered in a great need for effective delivery systems for such drugs. Two decades of studies of protein delivery from polymeric systems has revealed the great potential of gels that respond to environmental stimuli, such as temperature, pH, etc. Protein and peptide release can be engineered to occur in a pulsatile mode. The mechanism of this release is greatly affected by polymer design. 'Intelligent' amphiphilic copolymers emerge as a novel trend in the application of thermodynamically stable self-assembling lyophilic colloids to protein and peptide delivery.