In our studies of depth-dose profiles in water phantoms irradiated with neutrons used in radiotherapy, where we have employed a system of CR-39, LR 115 and Lexan plastics for recording the various types of charged particles produced in neutron interactions with tissue-equivalent materials, the need arose to establish the registration properties of low-energy heavy ions such as ¹²C, ¹⁴N and ¹⁶O in these plastics. Samples of Lexan and CR-39 were therefore exposed to low-energy ¹²C and ¹⁶O ions (0.05 – 0.65 MeV/nucleon) produced by the Harwell Tandem accelerator. We find that it is possible to produce etchable tracks of ¹²C and ¹⁶ions in this energy range in Lexan. We also report the etching characteristics of these tracks in both Lexan and CR-39.