We present a new pattern of nerve stimulation--double burst stimulation (DBS)--to detect residual neuromuscular block manually. The DBS consists of two short lasting, 50-Hz tetanic stimuli or bursts separated by a 750-ms interval. The response to this pattern of stimulation is two single separated muscle contractions of which the second is less than the first during nondepolarizing neuromuscular blockade. The ability to identify fade manually at different train-of-four (TOF) ratios was compared in four DBS patterns in which different numbers of impulses in the individual bursts were combined. The DBS with three impulses in each burst (DBS3,3) was considered to be the most sensitive and the least painful and thus most suitable for clinical use. The degree of fade in TOF and DBS3,3 was almost identical at any level of blockade (correlation coefficient 0.96), and the major post-DBS3,3 effect was a depression of the first twitch in TOF lasting less than 15 s. It is concluded that the DBS is more sensitive than the TOF in manual detection of residual block.