We prepared myofiber basal lamina sheaths (BLs) using the in vivo experimental procedure of Sanes et al. (J. Cell Biol.78, 176-198, 1978) on frog cutaneus pectoris muscle. On the 15 days post-operatively, acetylcholinesterase (AChE) is still found concentrated in native BLs and purified BLs preparations and both globular and asymmetric molecular forms coexist (Nicolet et al., J. Cell Biol., 107, 762-768, 1986). We describe here at least two distinct AChE pools, according to their differential solubility in non-ionic detergent and high-salt media. One is detergent-extracted (DE) and the other is detergent-insoluble, high-salt extracted (HSS). In the BLs preparation as well as in control motor end-plate rich regions (MEP-r) of muscle, both globular and asymmetric forms of AChE are found as DE and HSS variants. These observations suggest that all AChE forms are present in the extracellular muscle basal lamina and are bound through not only hydrophilic but also hydrophobic bonds, to probably distinct structural domains of the muscle basal lamina.