Abstract: Preactivated unsupported catalysts are prepared by contacting an unsupported olefin polymerization catalyst precursor with an activator, or co-catalyst in a suitable reaction medium and then contacting the mixture with additional solvent to form a preactivated unsupported olefin polymerization catalyst composition. The preactivated unsupported olefin polymerization catalyst composition is useful in a method of polymerizing an olefin monomer by adding it, in solution or slurry, to a gas phase polymerization reactor together with one or more olefins to form a polymer, copolymer, terpolymer, or the like. The use of the preactivated unsupported olefin polymerizaiton catalysts compositions does not plug the catalyst injection nozzle or feed tube when feeding the solution to the gas phase reactor.