Based on dry weight, first-order kinetics adequately describe the net decrease of RNA in Dictyostelium discoideum NC-4 until culmination, when a cessation of RNA degradation occurs. Between aggregation and sorocarp formation, the cells lose 40% of their RNA, or 19 mM-glucose equivalents expressed in terms of cell volume at aggregation. In sorocarps the spores contain a disproportionately large amount of RNA. Net RNA contents in sorocarps and in spores are unaffected by the availability of exogenous glucose. The relationship of dry weight, cell number and packed cell volume during differentiation is given.