| Name | Country | Market Cap (US$) |
|---|
| Oak-Bark Corporation | United States | Private |
| OGAWA SHOTEN, K.K. | Japan | Private |
| Ohio Coatings Company | United States | Private |
| Okamoto Sangyo K.K. | Japan | Private |
| Olein Recovery Corp | United States | Private |
| OLIFER-ACP SPA | Italy | Private |
| Omg America's Inc | United States | Private |
| Omya Clariana, S.A. | Spain | Private |
| Onduline Belgique SA | Belgium | Private |
| ONDULINE ITALIA SPA | Italy | Private |
| ONESTEEL MANUFACTURING PTY LIMITED | Australia | Private |
| ONESTEEL QUEENSLAND PTY LIMITED | Australia | Private |
| ONESTEEL TRADING PTY LIMITED | Australia | Private |
| Optimal Olefins (Malaysia) Sdn Bhd | Malaysia | Private |
| ORB ELECTRICAL STEELS LTD | United Kingdom | Private |
| Orelis | France | Private |
| Orenburgnefteprodukt | Russia | Private |
| Organizacion Terpel Bucaramanga S.A. | Colombia | Private |
| Oriento Industria e Comercio S.A. | Brazil | Private |
| Ortec Inc | United States | Private |
| ORYXE Energy International, Inc. | United States | Private |
| Osaka Petrochemical Industries Ltd. | Japan | Private |
| Outokumpu Chrome Oy | Finland | Private |
| Outokumpu Stainless AB | Sweden | Private |
| Ovako Forsbacka AB | Sweden | Private |
| Ovako Wire B.V. | Netherlands | Private |
| Owen Electric Steel Company Of South Carolina | United States | Private |
| Oxigenio do Brasil S.A. | Brazil | Private |
| Oxochimie | France | Private |
| OYAMA ISUZU CO.,LTD. | Japan | Private |
| OZKAN DEMIR CELIK SANAYI A S | Turkey | Private |
| P D V Midwest Refining L L C | United States | Private |
| PACMETAL SERVICES PTY LTD | Australia | Private |
| Palm-Oleo Sdn Bhd | Malaysia | Private |
| Palmetto Paving Corporation | United States | Private |
| Pan American Construction, Division of Apac Fl | United States | Private |
| PANDA STEEL INDUSTRIES INC. | Taiwan | Private |
| Pangang Group Sichuan Changcheng Special Company Limited | China | Private |
| Panzhihua Iron And Steel (Group) Co. | China | Private |
| PARALLOY LTD | United Kingdom | Private |
| Pav Republic Inc | United States | Private |
| Peckham Materials Corp | United States | Private |
| Pegasus Manufacturing Inc | United States | Private |
| Pennzoil Quaker State Canada Incorporated | Canada | Private |
| Petro Steel International, LLC | United States | Private |
| Petroferm U K Ltd | United Kingdom | Private |
| PETRONAS METHANOL (LABUAN) SDN BHD | Malaysia | Private |
| Petroquimica Rio Tercero S.A. | Argentina | Private |
| Pharmco Products, Inc. | United States | Private |
| Phenolchemie GmbH & Co. KG | Germany | Private |
| Philipp Brothers Chemicals, Inc. | United States | Private |
| Phillips Mfg And Tower Co (Inc) | United States | Private |
| Pinnacle Polymers | United States | Private |
| Pioneer Road Services Pty Ltd | Australia | Private |
| Plantar Siderúrgica S/A. | Brazil | Private |
| Pleissner Guss GmbH | Germany | Private |
| Pmp Fermentation Products, Inc | United States | Private |
| POLCHAR SP Z O O | Poland | Private |
| Polimeri Europa SpA | Italy | Private |
| POLIPACH BEIT SHEMESH ENTERPRISES (1991) LTD. | Israel | Private |
| Polymer Dynamics Inc | United States | Private |
| POSMMIT STEEL CENTRE SDN BHD | Malaysia | Private |
| Praxair Espana S.L. | Spain | Private |
| Preca CA | Venezuela | Private |
| Presswerk Krefeld GmbH & Co. KG | Germany | Private |
| Prista Oil Ad | Bulgaria | Private |
| Productos Chevron Texaco México, S.A. de C.V. | Mexico | Private |
| Productos Laminados de Monterrey, S.A. de C.V. | Mexico | Private |
| Produits Cari-All Inc, Les | Canada | Private |
| Profilstahl Delitzsch GmbH | Germany | Private |
| Progiven | France | Private |
| Progressive Processing Inc | United States | Private |
| Pronova Biocare AS | Norway | Private |
| PRT Rohrtechnik Nord GmbH | Germany | Private |
| Pudong Steel & Iron (Group) Co., Ltd. | China | Private |
| PUR-Systems GmbH & Co. KG | Germany | Private |
| Putie (Tianjin) Steel Processing Co., Ltd. | China | Private |
| Qingdao Iron & Steel Group Holding Co., Ltd. | China | Private |
| Quaker Chemical Indústria e Comércio Ltda. | Brazil | Private |
| Quaker State Corporation | United States | Private |
| Quest International Nederland B.V. | Netherlands | Private |
| Quimica Venoco, C.A. | Venezuela | Private |
| Químicos Industriales Peñoles, S.A. de C.V. | Mexico | Private |
| QUINTAIN STEEL CO., LTD. | Taiwan | Private |
| R E Pierson Materials Inc | United States | Private |
| R. & T. SWANN LTD | United Kingdom | Private |
| R.S.CLARE & CO.,LTD | United Kingdom | Private |
| RAILTECH INTERNATIONAL | France | Private |
| RATHI INDUSTRIES LIMITED | India | Private |
| Rayong Olefins Company Limited | Thailand | Private |
| ReClaim, Inc. | United States | Private |
| Regiomontana de Perfiles y Tubos, S.A. de C.V. | Mexico | Private |
| Republic Technologies International | United States | Private |
| RESIQUIMICA - RESINAS QUIMICAS, S.A. | Portugal | Private |
| REY-YANG STEEL CO., LTD. | Taiwan | Private |
| Reynolds Asphalt & Construction Company | United States | Private |
| Rgm Products, Inc. | United States | Private |
| Rhenus Lub GmbH & Co. KG | Germany | Private |
| Rhodia Filtec AG. | Switzerland | Private |
| Richland Research Corp | United States | Private |
|
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