X0303 4 2010-11-10 0 0001323885 AtriCure, Inc. ATRC 0001312548 Discovery Group I, LLC 191 N. WACKER DRIVE SUITE 1685 CHICAGO IL 60606 0 0 1 0 0001323510 Murphy Michael R C/O DISCOVERY GROUP I, LLC 191 N. WACKER DRIVE SUITE 1685 CHICAGO IL 60606 0 0 1 0 0001323511 Donoghue Daniel J C/O DISCOVERY GROUP I, LLC 191 N. WACKER DRIVE SUITE 1685 CHICAGO IL 60606 0 0 1 0 Common Stock 2010-11-10 4 P 0 8560 8.0927 A 1411447 I By Discovery Equity Partners, L.P. Common Stock 2010-11-10 4 P 0 1440 8.0927 A 241106 I By Pleiades Investment Partners - D, L.P Common Stock 2010-11-11 4 P 0 2868 8.05 A 1414315 I By Discovery Equity Partners, L.P. Common Stock 2010-11-11 4 P 0 482 8.05 A 241588 I By Pleiades Investment Partners - D, L.P Common Stock 2010-11-12 4 P 0 5537 8.0353 A 1419851 I By Discovery Equity Partners, L.P. Common Stock 2010-11-12 4 P 0 931 8.0353 A 242520 I By Pleiades Investment Partners - D, L.P Discovery Group I, LLC is the General Partner of Discovery Equity Partners, L.P., which is a discretionary client of the reporting person, that owns the reported securities. The reporting person disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest therein This transaction was executed in multiple trades at prices ranging from $8.06 to $8.10. The price reported above reflects the weighted average purchase price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected." Discovery Group I, LLC is an investment manager for Pleiades Investment Partners - D, L.P., which is a discretionary client of the reporting person, that owns the reported securities. The reporting person disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest therein. This transaction was executed in multiple trades at prices ranging from $8.00 to $8.05. The price reported above reflects the weighted average purchase price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected Michael R. Murphy and Daniel J. Donoghue are managing members of Discovery Group I, LLC, and each disclaims beneficial ownership of the reported securities except to the extent of his pecuniary interest therein. Micahel R. Murphy, Managing Director 2010-11-12 Daniel J. Donoghue 2010-11-12 Michael R. Murphy 2010-11-12