[Genetic factors and smoking habits].

To investigate whether genetic factors are involved in the maintenance of smoking habits, we examined restriction fragment length polymorphisms of cytochrome P-450 gene (P450 IIB1), one of the metabolizing enzymes of nicotine. The presence or the absence of polymorphic bands detected after digestion with Bam HI or Msp I was not related to smoking habits, the subjective degree of fondness for smoking and the subjective strength of addiction to smoking. Thus, we found no evidence for the involvement of this gene or adjacent gene(s) in the determination of smoking habits.