M achine assembly and motor component industries perceived as one of the industries which are potential in air contributing pollution. PT. Yamaha Motor Indonesia MFG is one of the industries which operates in the machine assembly and motor component, and has a. high potential in air pollution in the particle or dust form such as hazardous where Ne and Cr metals in the production process. Therefore, the factory of PT. Yamaha Motor Indonesia has been facilitated with particle or dust control tool. The objective of this research is to calculate the cyclone efficiency by measuring the particulate content on the cyclone input-output points of 13nd building (buffing) and also comparing the cyclone efficiency based on the tool dimension and the calculation formula according to Theodore de Paula forrnuJa.Thiis research was implemented in PT Yamaha Motor Indonesia MfG. which is located on Pulo Gadung Industry Sites, East Jakarta. The sample collecting was implemented on March 22nd to 301h 2005. Starting from 09:00-16.00. This research was implemented by using the buffing process. The sample collecting of particulate content was using the glass fiber filter, thus, it will be analyzed by using the gravymetric method. The measurement of particle diameter was using the particle size analyzer tool (PSA).Based on the field measurement, the cyclone efficiency of the sampling pp int of 28 cm are: on the first day : 86.71 %, on the second day: 85.075%, on the third day: 9'2.63o/o., on the fourth day : 81.10%, on the fifth day : 82.22%, on the sixth day : 83.62%. The cyclone efficiency of the sampling point 52 cm are : on the first day : 72. l 3o/o., on tbe second day : 89.47o/o., on the third day: 85.12%, on the fourth day: 83.21%, on the fifth day: 85.200/o., on the sixth day : 75.18%. The result of the effective tum (Ne) by using the Theodore de Paula formula, resulted 4.32. The dpc value is 12.4 µm. Thus, by using the PSA tool could.achieved the efficiency value for the sampling point of 28 cm is 85.60% and for the sampling point of5~ cm is 83.400/o.PT. Yamaha Motor Indonesia MFG is using cyclone as the particulate receiver with the diameter of 0.5 µm - 492 µm. and the gas that flow out of the outlet cyclone have a particle content of 0.5 µm - 492.47 urn, therefore, the gas will be carried to the bag house filter, in order to isolates the particle form the gas waste. After flowing out of the bag house filter, the gas have a low particle content.