The distribution of axoplasmic organelles at consecutive nodes of Ranvier was investigated light- and electronmicroscopically in horseradish peroxidase-transporting muscle nerve fibres of the adult cat. Three main and apparently temporally interrelated distribution patterns were noted. These patterns were referred to as A, B and C. The axoplasm of type-A and type-B nodes was highly segregated with regard to the proximodistal distribution of certain organelles. At type-A nodes horseradish peroxidase-positive membrane limited bodies and horseradish peroxidase-negative vesiculotubular membrane profiles were accumulated just distal and just proximal to the nodal mid-level, respectively. At B nodes a disc-like accumulation of enzyme activity, that was situated a few micron proximal to the mid-level, added to the type-A pattern. The type-C node showed a barely segregated axoplasm in which horseradish peroxidase-positive bodies were distributed randomly. We suggest, on the basis of the mutual order of the nodal types in a sequence of consecutive nodes and their appearance relative to the time after the administration of the HRP, that the different axoplasmic patterns reflect the operation of an ordered process that delays part of the retrogradely transported HRP for 2-3 days. The large number of lysosome-like HRP positive bodies that appeared at the nodes during this process indicates that the nodal axoplasm not only delays but also might take part in the degradation of the foreign protein.