A process for recovery of unreacted olefin monomer(s) from a particulate product of an olefin polymerization reactor, the process comprising: (a) supplying the particulate polymer product of an olefin polymerization reactor to a degassing vessel, wherein the particulate polymer product contains hydrocarbon impurities, including unreacted olefin monomer; (b) countercurrently contacting the particulate polymer product in the degassing vessel with at least a first gaseous stripping stream and a second gaseous stripping stream under conditions effective to strip hydrocarbon impurities from the polymer product and produce a first stripped polymer product; wherein the first gaseous stripping stream is recycled from (g), wherein the first gaseous stripping stream comprises at least 25% by weight unreacted olefin monomer and wherein the second gaseous stripping stream comprises less than 25% by weight unreacted olefin monomer; (c) countercurrently contacting the first stripped polymer product in the degassing vessel with an inert gas stream under conditions effective to strip hydrocarbon impurities from the first stripped polymer product and produce a second stripped polymer product; (d) recovering the second stripped polymer product from the degassing vessel; (e) removing from the degassing vessel a first gaseous effluent stream containing inert gas and hydrocarbon impurities, including unreacted olefin monomer, stripped from the particulate polymer product; (f) recovering unreacted olefin monomer from a portion of the first gaseous effluent stream; and (g) recycling a further portion of the first gaseous effluent stream to (b) as the first gaseous stripping stream. (a) supplying the particulate polymer product of an olefin polymerization reactor to a degassing vessel, wherein the particulate polymer product contains hydrocarbon impurities, including unreacted olefin monomer; (b) countercurrently contacting the particulate polymer product in the degassing vessel with at least a first gaseous stripping stream and a second gaseous stripping stream under conditions effective to strip hydrocarbon impurities from the polymer product and produce a first stripped polymer product; wherein the first gaseous stripping stream is recycled from (g), wherein the first gaseous stripping stream comprises at least 25% by weight unreacted olefin monomer and wherein the second gaseous stripping stream comprises less than 25% by weight unreacted olefin monomer; (c) countercurrently contacting the first stripped polymer product in the degassing vessel with an inert gas stream under conditions effective to strip hydrocarbon impurities from the first stripped polymer product and produce a second stripped polymer product; (d) recovering the second stripped polymer product from the degassing vessel; (e) removing from the degassing vessel a first gaseous effluent stream containing inert gas and hydrocarbon impurities, including unreacted olefin monomer, stripped from the particulate polymer product; (f) recovering unreacted olefin monomer from a portion of the first gaseous effluent stream; and (g) recycling a further portion of the first gaseous effluent stream to (b) as the first gaseous stripping stream.