Aciculin is a novel adherens junction antigen extracted from human uterine smooth muscle that is reported to associate biochemically with dystrophin. We attempted to determine (i) the immunostainability of anti-aciculin antibody for the 6 histochemically normal human muscles and seven muscles from boys with Duchenne muscular dystrophy (DMD) and 11 disease control muscles, (ii) the ultrastructural localization of aciculin in normal skeletal myofibers, (iii) aciculin's spacial relationship with dystrophin and beta-spectrin, and (iv) if the aciculin is ultrastructurally colocalized with dystrophin, the distance from the aciculin epitope to the epitope of the dystrophin N- or C-terminal domain. For this, rabbit anti-aciculin antibody was generated against the synthetic peptide of aciculin fragment D [4]. Immunohistochemical staining showed that the immunostainability of DMD muscles for anti-aciculin antibody was markedly decreased as compared with normal and disease control muscles. Single and double immunogold labeling electron microscopy of 6 histochemically normal human quadriceps femoris muscles revealed that aciculin was present along the inner surface of muscle plasma membrane and that aciculin formed doublets more frequently with dystrophin (23.5 +/- 1.8%; group mean +/- SE) than with beta-spectrin (12.8 +/- 1.1%; P < 0.01 two tailed t test). Rabbit anti-aciculin antibody frequently formed doublets with monoclonal antibodies against the N- or C-terminal domain of dystrophin at the muscle cell surface. These results suggest that aciculin is associated with dystrophin and may interact with both the N- and C-terminal domains of dystrophin.