High performance liquid chromatography (HPLC) is increasingly being used to estimate variant haemoglobins. A case of haemoglobin S/D (HbS/D) is presented, which was misdiagnosed as haemoglobin S/E (HbS/E) by HPLC. The patient was a 22 year old woman with sickle cell anaemia. Subsequent haemodilution by blood transfusion clearly elucidated the haemoglobin D peak on HPLC. Sample dilution experiments, using the pretransfusion sample, were done resulting in correct elution of the peak in the D window. Troubleshooting in similar problematic haemoglobin variant peaks seen on HPLC can be done by sample dilution.