製造早期參與新產品開發活動的相關理論指出，功能部門的整合可以增加組織資訊處理能力，提高績效，但只是概括性的觀念。而且新產品開發活動非常多，就成本面言，全面參與亦不見得有效。因此，製造單位應參與那些新產品開發活動才能提高開發績效，實值探討。 本研究之主要構念的變項均經實地調查訪談，並經產業領導廠商確認。並以汽車零組件業為研究對象，經由人員訪談，收集139份有效問卷，藉由因素分析、集群分析、以及t檢定後，發現製造早期參與新產品開發活動和製造績效中的計劃達成率有關，但對於品質、生產力並無顯著相關。 此外，更進一步研究則發現，受訪廠商在產品技術情報收集、市場需求調查、規格調查、財務／協力廠生產可行性分析、生產線／設備／品質基準規格規劃、測試等活動，若製造單位的參與程度較高，則其績效亦顯著提高。 最後，本研究建議，廠商下游單位全面參與上游的設計開發活動並不見得可以提高下游的績效，而是參與產品企劃，以期在產品設計之前，將製造單位的限制、能力納入產品設計的考量，提高產品易製性；製造單位參與測試，能立即回饋設計的缺失，縮短產品開發時間，提升生產新產品的生產力。

The Early Manufacturing Involvement (EMI) theory has indicated that functional integration can increase the organization’s information processing capability, hence improving performance. However, the theory is only a conceptual description or built upon case study. It lacks of enough empirical researches to verify such a theory. Besides, the new product development （NPD）process includes so many activities. The data were collected by interviewing managers of the R&D and Operation of the major Taiwanese Auto-Parts company. 139 usable structured questionnaires were collected. The major findings are as following: he degree of EMI is not significantly correlated with the manufacturing performance of NPD. The manufacturing department in sample firms with higher manufacturing performance of NPD involve more in activities of product planning stage and product testing stage. The research suggests firms of Taiwanese Auto-Parts that total involvement of down stream in the up stream activities can not at all increase the down stream performance. The manufacturing department can involve the product planning, testing stage to increase its NPD performance.