For diesel emission control technologies, reduction efficiencies of Particulate Matter (PM) control systems have been traditionally reported based on mass-based criteria. However, particle number-based criteria are now receiving increased attention. In this paper, results of real-time particle size distribution and number based evaluation of the effectiveness of multiple PM control technologies are reported on an HDD engine. An Engine Exhaust Particle Sizer (EEPS) was used for comparative analysis. The technologies that were evaluated included diesel oxidation catalysts (DOC), a DOC with an uncatalyzed wall-flow filter as a continuously regenerating diesel particulate filter (CR-DPF) system, a DOC with a catalytically coated wall-flow filter as a catalyzed CR-DPF (CCR-DPF), and a DOC with a partial filter as a continuously regenerating partial filter (CR-PF). Engine testing was performed using transient Federal Test Protocol (FTP) cycles using both ultra low sulfur diesel (ULSD) and low sulfur diesel (LSD) on a MY2000 Cummins ISM 350ESP test engine. Particle number-based reduction efficiencies were compared with mass-based efficiencies. With ULSD fuel, the CR-DPF and CCR-DPF demonstrated high reduction efficiencies using both mass-based and number-based methods, while the DOC and CR-PF showed higher mass-based reduction efficiencies when compared to number-based efficiencies. With LSD fuel, the DOC and CR-PF showed higher number-based reduction efficiencies when compared to mass-based efficiencies. The CR-DPF and CCR-DPF were highly effective at reducing both nuclei mode particles and accumulation mode particles. The higher number based reductions for DOC and CR-PF with LSD fuel are likely due to the suppression of sulfuric acid nuclei mode particles, which are present in higher quantities with the engine operating with LSD compared to ULSD.