An interesting feature of the muscular organization of the human hand is that the main flexors and extensors of the fingers are compartmentalized and give rise to multiple parallel tendons that insert onto all the fingers. Previous studies of motor unit synchrony in extensor digitorum (Keen and Fuglevand 2004b) and flexor digitorum profundus (Reilly et al. 2004; Winges and Santello 2004) have indicated that synaptic input to motor neurons supplying these multi-tendoned muscles is not uniformly distributed across the entire pool of motor neurons but instead appears to be partially segregated to supply subsets of motor neurons that innervate different muscular compartments. Little is known, however, about the organization of the synaptic inputs to the motor neurons supplying another multi-tendoned finger muscle, the flexor digitorum superficialis (FDS). Therefore, in this study, we estimated the extent of divergence of last-order inputs to FDS motor neurons by measuring the degree of short-term synchrony among motor units within and across compartments of FDS. The degree of synchrony for motor unit pairs within the same digit compartment was nearly double that of pairs of motor units in adjacent compartments and more than four times that of pairs in nonadjacent compartments. Therefore, like other multi-tendoned muscles of the hand, last-order synaptic inputs to motor neurons supplying the FDS appear to supply predominately subsets of motor neurons innervating specific finger compartments. Such an organization presumably enables differential activation of separate compartments to facilitate independent movements of the fingers.