Two casting examples are given in this article showing that shrinkage problems in the castings were solved using proportional solidification theory, specially using thin, wide and short rectangular riser neck. And computer solidification simulation for castings was also discussed. Computer solidification simulation software as a high technology is a powerful tool for helping foundry engineers in improving process design of casting, casting quality, and casting yield. However it is misunderstanding that expecting to get solution and solve (casting) problem immediately using casting simulation software. Computer solidification simulation software as a tool for castings can play good role, reach expected result and potential only when used by experienced casting experts. Combination of computer solidification simulation software, expert system and artificial (knowledgeware) would be better to solve problems about process design of castings.