This investigation addressed the processing of ultrafine tailings (slimes) from an iron ore concentrator via reverse cationic flotation to produce pellet feed fines, despite the traditional view that ultrafine particles do not float. Following size analyses, chemical and mineralogical characterisation, desliming and flotation tests were performed aiming at verifying the flotation behaviour of the slimes. Different dosages of collector and depressant were used. The promising results of the laboratory scale tests led to carrying out pilot scale tests with the currently produced slimes, and the slimes that will be generated in the future, after the commissioning of the mining company's expansion project. It was observed that a reverse cationic column flotation process, using high depressant dosage, was selective, yielding high grade concentrates with low impurity content at high levels of iron recovery, approximately 60% mass recovery and 80% metallic recovery in the flotation stage. Excellent valuable product grade (less than 1% silica) and reject product grade (approximately 12% iron) were achieved, resulting in high selectivity levels. The overall mass recovery reached 20%. (C) 2010 Elsevier Ltd. All rights reserved.