The resting lymphocytes of patients with chronic lymphocytic leukaemia (CLL) contain the same amount of RNA as do those of normal individuals, and in terms of different molecular species, as analyzed by polyacrylamide gels, there is very little to distinguish the leukaemic cells. However, a relatively large amount of low molecular weight RNA, similar to the SnRNA found in several other tissues, is present in the CLL cells. The products of transcription of the leukaemic cell nucleus have been studied by the incorporation of labelled uridine and methionine. The leukaemic lymphocytes show a build-up and apparent delay in processing of ribosomal RNA precursor, when compared to normals, but studies of methylation reveal that the production of mature ribosomal RNA occurs at a normal rate. The nature of the stable high molecular weight material produced is now being studied. The production of proteins on the ribosome of CLL cells seems likely to be faulty, as evidenced by the deficiency of active ribosomes in the leukaemic cells. Studies with selective inhibitors will show whether this is due to some fault in transcription of messenger RNA.