Fibroblasts cultivated in three-dimensional lattices exhibit a large decrease of protein synthesis, mainly through transcriptional control. However, no previous work was devoted to a potential ribosomal regulation. We evaluated ribosomal ribonucleic acid (RNA) in monolayer- and collagen lattice-cultured fibroblasts. After one week of culture, total RNA was 60% lower in lattice-cultured fibroblasts than in monolayer-cultured cells. The decrease was identical for 18 S and 28 S rRNA subfractions. The half-life of RNA was much shorter in collagen lattice-cultured fibroblasts than in monolayers. These results suggest that protein synthesis in lattice-cultured fibroblasts is partly regulated at the ribosomal level.