Transgenic insect-resistance cultivars expressing insecticidal toxicants, δ endotoxin of Bacillus thuringiensis, inhibitors of proteases and lectin, etc., for insect pest control are a new innovation, inspiring scientists and farmers to combat agricultural pests. Use of transgenic plants to combat pests is a modified application of classical host plant resistance. However, there are many problems and risks concerning food safety and environmental conservation. Transgenic technologies, protoplast transformation, particle bombardment and Agrobacterium methods have been established and successfully used for producing transgenic plants. However, non-target genes or unnecessary DNA fragments are often introduced to the crop. For instance, marker genes such as antibiotics or fungicidal resistant genes are also introduced and their behaviors and environmental effects are unknown. Generating marker-free transgenic plant is very important, as was reported by Sugita et al. (1999). On the other hand, the use of gene transformation in insects can contribute to the development of new natural enemies, as well as a better understanding of insect genetics, biochemistry, development and behavior. Further studies on the effects on transgenic plants for food safety and environmental conservation are needed. The technologies for pesticide, safety evaluation, which have been long studied, should contribute to the safety studies of transgenic crops.