This study examined preservice teachers' understanding of biotechnology and its related processes. A sample comprised 88 elementary education preservice teachers at a large university in the Midwest of the USA. A total of 60 and 28 of the participants were enrolled in introductory and advanced science methods courses, respectively. Most participants had taken two integrated science courses at the college level. Data were collected using a questionnaire, which had open-ended items and which required participants to write the definitions and examples of the following terms: biotechnology, genetic engineering, cloning and genetically modified foods. The results indicate that preservice teachers had limited understanding of biotechnology and its related processes. The majority of the preservice teachers provided poor definitions, explanations, and examples of biotechnology, genetic engineering and genetically modified foods. Surprisingly, however, a moderate number of preservice teachers correctly defined cloning and provided correct examples of cloning. Implications for science teacher education, science curriculum, as well as recommendations for further research are discussed. (Contains 3 tables.)