  We present results of an ongoing survey of low surface brightness planetary
nebulae (PNe). Using both narrow-band imaging and long slit spectroscopy we
have studied 15 new examples for interaction with the interstellar medium (ISM)
demonstrating that this process is common in evolved PNe. Characteristic
properties of the nebulae in terms of morphology and plasma parameters have
been established and different degrees of interaction can be identified.
Although the study of the objects is at an early stage the observational
findings are in agreement with theory. The data indicate that the objects have
a very high degree of individuality due to the action of complex physics under
varying conditions.
