Polymeric materials have the advantage of light weight, ease of manufacturing and feasibility for various shapes, compared with porcelain one. Application of the polymeric materials to outdoor electrical insulating apparatuses has achieved to reduce the size, weight of the equipments, and maintenance cost of the electrical power lines. Especially, silicone rubber can show good weatherability and hydrophobicity, so that it has been widely applied to polymeric insulators for outdoor use. Polymeric insulators are gaining market share as a result of improved tolerance to pollution, ease of handling and installation. In this article, the state of research and development of the polymeric insulators and their application for the electrical power lines are provided.