This article documents how log analysis can inform qualitative studies concerning the usage of web-based information systems (WIS). No prior research has used http log files as data to study collaboration between multiple users in organisational settings. We investigate how to perform http log analysis; what http log analysis says about the nature of collaborative WIS use; and how results from http log analysis may support other data collection methods such as surveys, interviews, and observation. The analysis of log files initially lends itself to research designs, which serve to test hypotheses using a quantitative methodology. We show that http log analysis can also be valuable in qualitative research such as case studies. The results from http log analysis can be triangulated with other data sources and for example serve as a means of supporting the interpretation of interview data. It can also be used to generate hypotheses, which were otherwise unthinkable. We suggest that log data be included as a main data source in the field of computer supported cooperative work, information systems, and computer-mediated communication, in order to help clarify the role of the technology related to concepts like coordination, task analysis, or communication.