There is evidence that the shape of cells and their contact with a matrix direct the growth and the differentiation of both normal and cancer cells. Cells in 3D culture resemble the in vivo situation more closely than do those in conventional 2D cultures. We have studied the interactions and functions of B16F10 mouse melanoma cells, which spread and grow well on tissue culture polystyrene (tPS), when they were made to aggregate on cellulose-coated Petri dishes (CEL). This aggregation of melanoma cells on CEL was Ca2+ dependent and mediated by N-cadherins. The levels of N-cadherin and beta-catenin transcripts in cells cultured on CEL and tPS were similar, but those on CEL contained less beta-catenin protein. Immunoprecipitation and immunostaining showed that both N-cadherins and beta-catenins were present at the membranes of cells on CEL. Cells proliferated significantly more slowly after 48 h on CEL and the cellulose coating caused most of them to arrest in G1. We also compared the melanin contents and tyrosinase activity of cells on CEL and controls grown on tPS. Melanogenesis was induced in cells aggregated on CEL. A cellulose substrate thus appears to be an outstanding tool for studying cell-cell interactions and cell functions in 3D cultures.