A composition suitable for injection through a needle ranging in diameter from 0.838 mm to 0.413 mm (18-22 gauge) into a host, comprising: microparticles comprising a biologically active agent dispersed or dissolved within a polymeric binder in an aqueous injection vehicle, wherein (a) said microparticles are suspended in said injection vehicle at a concentration of greater than 30 mg/ml to form a suspension and have a mass median diameter of at least 10 μm and less than 250 μm, (b) a fluid phase of said suspension has a viscosity of at least 50 cP at 20 °C, (c) the biologically active agent is a peptide, (d) the polymeric binder is selected from the group consisting of poly (glycolic acid), poly-d, 1-lactic acid, poly-1-lactic acid, and copolymers of the foregoing,, and (e) the aqueous injection vehicle comprises (i) a viscosity enhancing agent selected from sodium carboxymethyl cellulose, polyvinylpyrrolidone and hydroxypropylmethylcellulose; (ii) a tonicity adjusting agent comprising sodium chloride; and (iii) a wetting agent selected from polysorbate 20, polysorbate 40 and polysorbate 80, but is not the aqueous vehicle consisting of 3% by volume sodium carboxymethyl cellulose, 1% by volume polysorbate 20, 0.9% by volume sodium chloride, and a remaining percentage by volume of water. microparticles comprising a biologically active agent dispersed or dissolved within a polymeric binder in an aqueous injection vehicle, wherein (a) said microparticles are suspended in said injection vehicle at a concentration of greater than 30 mg/ml to form a suspension and have a mass median diameter of at least 10 μm and less than 250 μm, (b) a fluid phase of said suspension has a viscosity of at least 50 cP at 20 °C, (c) the biologically active agent is a peptide, (d) the polymeric binder is selected from the group consisting of poly (glycolic acid), poly-d, 1-lactic acid, poly-1-lactic acid, and copolymers of the foregoing,, and (e) the aqueous injection vehicle comprises (i) a viscosity enhancing agent selected from sodium carboxymethyl cellulose, polyvinylpyrrolidone and hydroxypropylmethylcellulose; (ii) a tonicity adjusting agent comprising sodium chloride; and (iii) a wetting agent selected from polysorbate 20, polysorbate 40 and polysorbate 80, but is not the aqueous vehicle consisting of 3% by volume sodium carboxymethyl cellulose, 1% by volume polysorbate 20, 0.9% by volume sodium chloride, and a remaining percentage by volume of water. (a) said microparticles are suspended in said injection vehicle at a concentration of greater than 30 mg/ml to form a suspension and have a mass median diameter of at least 10 μm and less than 250 μm, (b) a fluid phase of said suspension has a viscosity of at least 50 cP at 20 °C, (c) the biologically active agent is a peptide, (d) the polymeric binder is selected from the group consisting of poly (glycolic acid), poly-d, 1-lactic acid, poly-1-lactic acid, and copolymers of the foregoing,, and (e) the aqueous injection vehicle comprises (i) a viscosity enhancing agent selected from sodium carboxymethyl cellulose, polyvinylpyrrolidone and hydroxypropylmethylcellulose; (ii) a tonicity adjusting agent comprising sodium chloride; and (iii) a wetting agent selected from polysorbate 20, polysorbate 40 and polysorbate 80, but is not the aqueous vehicle consisting of 3% by volume sodium carboxymethyl cellulose, 1% by volume polysorbate 20, 0.9% by volume sodium chloride, and a remaining percentage by volume of water.