Scanning transitiometry, a newly developed version of pVT-controlled scanning calorimetry, has been used to investigate the thermodynamic behavior of asphaltenic fluids under in-well pressure and temperature conditions. The use of the technique, which allows measurements over extended T and P ranges, is shown to be suitable to induce phase changes in aliphatic systems during various scans of the three variables p, V, and T. Extension of the technique to asphaltenic fluids shows its potential to investigate such complex systems, as already observed with polymer materials. Successive compression/decompression cycles performed on an asphaltenic fluid confirm that both flocculation and solubilization. in such systems are governed by slow kinetic phenomena.