A set of procedures for diagnosis and evaluation of flotation plants is presented. Flotation plants have been characterised in terms of the hydrodynamic and metallurgical performance of each circuit stage. This approach is the result of 20 years of flotation research at Santa Maria University. The hydrodynamic approach consists of using radioactive tracers for measuring the effective residence time distribution of liquid, solids per size class and gas. These tests allow the identification of the flow regime (dispersion)and effective cell volume occupied by liquid, solid and gas. Solids segregation (per sizeclass) was evaluated by measuring the axial solids percent profiles. The gas dispersion was evaluated by measuring bubble size distribution and superficial gas rate, below the pulp-froth interface (quiet zone). Thus, the bubble surface area flux SB (m2/s/m2) was estimated. A new methodology for measuring the effective froth transport times of liquid, floatable mineral, and gangue per size class, using radioactive tracers, was developed and evaluated in large size cells. Flotation metallurgical performance was characterised using a short cut method, including sampling of the first cell of flotation banks, to identify the flotation rate parameters. Evaluation of the froth recovery (true flotation), by bubble load measurement, allowed the characterisation of the collection and froth zones performance, independently.A new approach to identify the actual flotation rate distribution (collection zone) in industrial cells, using radioactive tracer tests and the gamma function, was developed.The above methodologies have been applied for testing industrial flotation circuits with different cell sizes, from 45 to 300 m3. It was shown that this approach is a powerful tool for flotation circuit diagnosis, to evaluate the effect of design and operating variables upon cells and circuit performance, as well as to identify the fundamental scale-up factors in large flotation cells.