Impact is generally defined as any change or outcome resulting from an activity. In case of scientific research publications are the quantifiable outcome of the research process. The presentation will therefore focus on electronic publication impact as a limited but rather well defined sub-field of research impact. Publication impact can be measured by author or reader generated indicators. Author generated indicators would be citations. Reader generated indicators would be usage. Usage data can be collected through webserver or linkresolver logs. It has to be normalized in order to be shared and analyzed meaningfully. There are some initiatives to provide a suitable infrastructure including publisher data (COUNTER/SUSHI) and data collected through open access repositories. Citation as well as usage data can be analyzed quantitatively or structurally. These analyses can be combined or complemented to create new metrics to add to the ISI impact factor (IF).