We have performed a detailed quantitative analysis of the transcription and accumulation of ribosomal RNA and ribosomal protein mRNA in the ciliated protozoan Tetrahymena thermophila during changes in growth conditions, and found that: (1) nutritional downshifts lead to a rapid decrease in transcriptional activity whereas nutritional upshifts lead to rapid restoration of transcriptional activity, (2) starvation leads to decreased translation of ribosomal protein mRNA and (3) the rate of ribosomal protein mRNA degradation decreases after a nutritional upshift. We present evidence that the proximal promoters of two ribosomal protein genes and the ribosomal RNA gene compete for binding of nuclear factor(s) in vitro, suggesting that the coordinated regulation of these genes may involve a common set of transcriptional regulators.