Node-to-node heterogeneity of reaction and recognizable patterns of reaction in node groups draining melanoma were sought. Nodes from 72 patients undergoing lymphadenectomy for high-risk, primary melanoma (57) or node-spread melanoma (15) were accurately oriented to the nearest melanoma. Reactivity of paracortex, follicular areas, and sinuses was assessed on a 0-3+ scale. Reactivity was prominent in paracortex and sinuses but varied from node to node within node groups. Nodes nearest to tumor showed least reaction; nodes at intermediate distances from tumor were most reactive, while those farthest away showed mostly little reaction. Variation of nodal reaction that correlated with the node position relative to the nearest melanoma (zoned reaction) was seen in 92% of patients with nodal metastases of melanoma and in 64% of patients with primary malignant melanoma. Follicular and sinusoidal reactions showed no significant zoning. S-100 protein-positive paracortical dendritic cells (PDCs) in tumor-oriented nodes were quantified. PDCs were infrequent in nodes partly replaced by melanoma or located near to melanoma but were numerous in nodes located farther from tumor. Changes of nodal activity (relative stimulation or suppression) correlate with the distance of the node from the nearest deposit of primary or metastatic melanoma.