As part of the Warm Core Rings Experiment, a set of intensive observations of thermohaline intrusions at the outer edge of a warm ring were obtained. The observations included a CTD tow-yo, repeated microstructure profiles and continuous acoustic Doppler velocity measurements. The survey was performed relative to the drift of a drogued surface buoy. The CTD data allowed us to map the three-dimensional structure of the intrusive features. The data indicate that the core of a cold, fresh intrusion became lighter as it extended across the front. This is contratry to the usual expectation that such intrusions get denser under the influence of salt fingers. An explanation for this apparent behavior can be found in the microstructure profiles, which suggest that the diffusive interfaces associated with the intrusion are the dominant mixing process, since they are more strongly unstable and reveal higher turbulence levels than nearby fingering regions. Clear signatures of double-diffusive mixing are seen in the fine- and microstructure data; however, the turbulent dissipation in the diffusive layers was not as high as the laboratory flux laws predict and shear-driven turbulence may be the stronger mixing mechanism. Double doffusion clearly plays some role in mixing the intrusive features but its role in actually generating the intrusion remains ambiguous, given the tendency of warm-core rings to wrap “streamers” of shelf, slope and Gulf Stream waters around themselves.