We use administrative data linking workers and firms to study employer-to-employer (E-to-E) flows. After discussing how to identify such flows in quarterly data, we investigate their basic empirical patterns. We find that the pace of E-to-E flows is high, representing approximately 4% of employment and 30% of separations each quarter. The pace of E-to-E flows appears to be highly procyclical and varies systematically across worker, job, and employer characteristics. There are rich patterns in terms of origin and destination of industries.