In classical incremental redundancy (IR) hybrid ARQ schemes, successive retransmissions consist of different redundant versions of the same message. This paper investigates the improvements that may result by jointly coding across several data packets, in order to create redundancy packets relative to multiple messages. Theoretical analysis as well as simulation results suggest that multiple-packet IR may offer substantial throughput gains with respect to the classical, single-packet IR approach, particularly at medium-to-high signal-to-noise ratio.