Summary. IVS‐2–654 C → T is a common Chines β‐thalassaemia mutation. Previous studies report that this mutation resulted in the formation of an abnormally spliced mRNA and the absence of detectable normal β‐globin mRNA, hence the mutation was considered to cause βd́; ‐ thalassaemia. We recently used the method of PCR amplified cDNA copies of circulating erythroid cell mRNA to analyse the mutant gene transcripts and found that this IVS‐2–654 mutation does not abolish normal RNA processing entirely, but that a significant amount (over 15%) of normally processed β‐globin mRNA is produced. Microglobin chain biosynthetic analysis using the HPLC method showed that β‐globin chain was also present in the blood of patients with IVS‐2–654 C → T mutation. Accordingly, this mutant allele leads to a β+‐thalassaemia. Further, the methodology described in this paper provides a new approach towards the detection of RNA transcripts in β‐thalassaemia and other genetic diseases.