In this study, the disintegration of a liquid by a rotary atomizer is characterized. Correlations of the relevant variables with regard to spray performance were experimentally investigated. Seven variants of a rotary atomizer with an in-line array of injection orifices were evaluated. The diameter of the injection orifice was varied from 1 to 5 mm, and the number of injection orifices was varied from three to 12. The droplet size, velocity, and spray distribution were measured using a phase Doppler particle analyzer system, and the spray was visualized using Nd-Yag laser flashed photos. In the visualization, three spray patterns were observed. Ligament spray was observed with the small orifice diameters of 1 and 2 mm. A liquid film breakup pattern was observed over most of the experimental conditions. In some cases, at a low rotational speed or a high mass flow rate, irregular spray patterns were observed. From the droplet size measurements, the shapes of the liquid columns and liquid films generated from the in-line injection orifices played important roles in the liquid drop size. Considering the relationships between the measured droplet sizes and the relevant variables, the primary variable affecting droplet size was liquid film thickness. Consequently, we obtained correlations between the nondimensional droplet size and the nondimensional theoretical liquid film thickness.