A method of making discrete, closed-cell, alkenyl aromatic polymer foam packing bodies comprises: (a) heating polymer material consisting of more than 50wt.% monomer units; (b) forming a foamable gel by incorporating into the melt polymer material obtd. in step (a), a blowing agent; (c) extruding the gel through a die to an area of reduced pressure to form a polymer foam strand; (d) pelletising to form foam bodies; and (e) expanding the bodies by exposing them to heated air or stream.    The blowing agent has 20 wt.% or more, based on the total wt. of agent, of a first blowing agent selected from CO2, ethane and their mixts. The agent is incorporated at high pressure.    Also claimed are the following: (1) a method in which at step (c), a continuous strand of gel is formed, which is then pelletised to form a number of strands; the strands being expanded in an area of reduced pressure to form a number of foam bodies which are then treated as at step (e); (2) a method as described in the main claim, in which a further step (4) includes moulding and coalescing the foam bodies to form an article; (3) a method as in (1), in which step (d) is omitted and the foam strands are expanded by heating them in air or steam, followed by a step of intermittently severing the continuous strands to form discrete foam strands; and (4) a method as in (3) in which the continuous foam strands are severed intermittently and the discrete strands formed are further expanded by exposing them to heated air or steam.    USE/ADVANTAGE -   The foam bodies are primarily useful for loose-? applications. A number of the foam bodies can be moulded and coalesced or adhered to form articles such as insulation board. Also, the foam body can be ground into scrap for use as blown insulation. The use of CO2 and/or ethane as blowing agents allows the redn. of elimination of VOCs which are currently used. This redn. or elimination is environmentally desirable. Foam body densities of less than 16 kg/m3 can be achieved (claimed). The average cell size is 0.03-2.0 mm. according to ASTM D3576, and the foam is most pref. less than 2% open cell (ASTM D2856-A) (claimed).