Abstract: A brief introduction to the in situ hybridization technique is followed by a review of its current application status in plant genetics and breeding: ( 1 ) monitoring of alien chromatin and chromosome distortion; (2) gene engineering and gene expression; (3) construction of plant DNA physical map; (4) study on chromosome RNA and some other fields. Opinions on the development of the in situ hybridization technique in the future, especially with respect to the improvement of resolution, combination of in situ hybridization with chromosome banding, and PCR in situ hybridization are put forward as well.