From the mid-1960s, New Left leaders began engaging with foreign Communist officials, creating networks that were sometimes public and sometimes clandestine. While American activists retained agency and were not under the control of foreign powers, these relationships involved influence, collaboration, and foreign involvement that were sufficient to trigger legitimate counterintelligence (CI) concerns. The FBI and other agencies monitored these interactions using human, signals, and open-source intelligence, even as internal and political pressures led some observers to overemphasize control or foreign financing as benchmarks for threat. Declassified documents and memoirs indicate that foreign involvement existed, though often modest and non-controlling, and that the Bureau had intelligence-based reasons for its investigations. The chapter emphasizes that while the FBI often abused its authority through dragnet surveillance and coercive tactics (e.g., COINTELPRO), its CI activities were not solely arbitrary; they reflected real, if sometimes exaggerated, concerns about activist leaders’ international connections. The chapter closes by underscoring the value of further research, both to clarify the extent of foreign influence on the New Left and to better understand the intelligence, institutional, and political dynamics that shaped FBI decision-making during this period.