Use of thermodynamic data has been amongst the most reliable of tests for determining the nature of transitions for all materials. Polymers exhibit several solid-state transitions whose origin is often unknown. Some of these are undetectable with commercially available rapid-scanning calorimeters. These unresolved transitions of interest range from (1) glass transitions whose ΔCp is significantly reduced by the presence of crystallinity to (2) transitions connected with polymorphism in polymers, (3) sub-glass transitions detectable by other methods, (4) multiple melting and glass transitions. An existing calorimeter has been suitably modified to obtain high precision thermodynamic data. In this report we review briefly, with limited discussion, some recent results in this area.