Many open source and commercial developers practice contemporary code review, a lightweight, informal, tool-based code review process. To better understand this process and its benefits, we gathered information about code review practices via surveys of open source software developers and developers from Microsoft. The results of our analysis suggest that developers spend approximately 10-15 percent of their time in code reviews, with the amount of effort increasing with experience. Developers consider code review important, stating that in addition to finding defects, code reviews offer other benefits, including knowledge sharing, community building, and maintaining code quality. The quality of the code submitted for review helps reviewers form impressions about their teammates, which can influence future collaborations. We found a large amount of similarity between the Microsoft and OSS respondents. One interesting difference is that while OSS respondents view code review as an important method of impression formation, Microsoft respondents found knowledge dissemination to be more important. Finally, we found little difference between distributed and co-located Microsoft teams. Our findings identify the following key areas that warrant focused research: 1) exploring the non-technical benefits of code reviews, 2) helping developers in articulating review comments, and 3) assisting reviewers' program comprehension during code reviews.