Research has taken place in various most important production lines of the Slovene chemical and process industries. It has included process analysis, modelling and process optimization (from technological and environmental point of view) of several selected industrial production lines, such as: Nafta Lendava, Lek Ljubljana, Krka Novo mesto, Belinka Ljubljana, TKI Hrastnik, Tanin Sevnica in Steklarna Rogaška; all of them are due to size and nature bound to so called IPPC directive. This directive requires modernisation to the BAT extent of clean technologies (prescribed in BREF documents). In some most complicated cases mathematical modelling was combined or replaced with pilot tests. By this means the diversion of actual operating performances from theoretically calculated or experimentally determined were established. Critical production steps were then determined in each of the noted industries, and new optimal conditions proposed. In the case od new products/ processes, optimal technological process was presented with respect to yield and environmental impact. Another approach towards introduction of sustainable industrial development, that is complementary to formal chemical engineering calculations, is a proactive emvironmetal management system, based on the Cleaner Production methodology (UNEP, EUREKA). This has been upgraded, adapted for the Slovene conditions and tested in three different groups of companies (altogether 32) from various branches of economy. Regardless to the type of industry and level of technological development large saving were achieved in process material and energy consumption, media reuse and recycling, reduction in waste and emission generation etc.