A Practice Note discussing strategies for defending against control person claims under the federal securities laws. This Note distinguishes controlling person claims from other theories of secondary liability, including aiding and abetting, conspiracy, and respondeat superior. It explains the requirements for pleading and proving control person liability claims under Section 15 of the Securities Act of 1933 and Section 20 of the Securities Exchange Act of 1934 and provides practical guidance for counsel challenging a plaintiff's claim through a motion to dismiss or motion for summary judgment.