The anatomical characteristics of the accumulation of dopamine β hydroxylase (DBH) that occurs after ligation of rat sciatic nerve were examined in detail using a recently developed specific immunofluorescence method. Although rapid accumulation of DBH occurred showing the presence of axonal transport, the anatomical observations indicated that the build up was considerably more complex than the sample 'blockade' model frequently used as a basis for computation of transport rates from quantitative estimates of accumulation. During the early time period (7 hr) the situation was complicated by a substantial amount of accumulation of DBH distal to the ligation. By 24 hr after ligation the digital accumulation was small compared to that present proximally. The size of the discrete area covered by DBH fluorescence at 24 hr indicated that axonal membranes may have already started to rupture, thus releasing vesicles into the extracellular space. By 48 hr after ligation the DBH was no longer confined to the area near the ligation, but extended 3.6 mm proximally. By 96 hr after ligation there had been a net loss of DBH fluorescence indicating that degradation and clearance of accumulated DBH had occurred.