The appropriate management of haematological disorders must rely on a precise and long-term monitoring of the patient's response to chemotherapy and radiotherapy. Clinical data are not sufficient and that is why in the last decade it became the most important to improve the knowledge of haematological diseases on the basis of molecular techniques and molecular markers. The presence of residual malignant cells among normal cells is termed minimal residual disease (MRD). Nowadays a great progress has been made in the treatment of malignant diseases and in the development of reliable molecular techniques, which are characterised by high sensitivity (10?3? 10?6) and ability to distinguish between normal and malignant cells at diagnosis and during follow-up. Especially, MRD data based on quantitative analysis (RQ-PCR, RT-RQ-PCR) appear to be crucial for appropriate evaluation of treatment response in many haematological malignancies. Implementation of standardized approaches for MRD assessment into routine molecular diagnostics available in all oncohaematological centres should be regarded nowadays a crucial point in further MRD study development.