We investigate the kinds of questions asked by environmental scientists. To this end, we describe the orientation of scientific research by posing four questions: What is the lack of knowledge to be addressed by the research? What is the purpose of the results? What are the subjects the research is dealing with? What are the methods chosen for the investigation? We propose that problem-oriented environmental science should strive to find answers to these questions that are different from those offered by "classical" natural sciences. As a focus of our study, we select four fields where the answers to the orienting questions are relevant: (1) reflexivity and "reflexive science" (Ulrich Beck), (2) dealing with uncertainty and missing knowledge, (3) competing internal scientific goals and external orientations such as sustainability, (4) the relationship between environmental sciences and politics. As a case study, we investigate the historical development of ecological chemistry. This development can be divided into three phases: an initial phase, an independent phase, and a re-orientation phase. Different internal and external orientations governed the scientific research in these three phases. This example provides insight into the problem of competing internal and external orientations; as a possible solution, we propose a scientific orientation open to societal concerns (to be continued in a follow-up paper by Boeschen et al. 2001 in GAIA 10(3), pp. 203-212).