[en] Although new work has generally reinforced the previous conclusions (1985), recent sheets of commercial grade CR-39 have exhibited both good neutron sensitivity, and low backgrounds, which, unlike those of earlier batches, have not increased with time. This improvement is believed to be associated with changes in the manufacturing process. In addition, this work has confirmed that a revised and simplified processing schedule produces equivalent results to the original processing schedule, and there are indications that further changes may improve the low-energy neutron response without increasing the backgrounds. Some studies of the effect of time and environment on the neutron sensitivity and background in the plastic have been undertaken. These have shown that, although slow changes take place in the plastic with time and environment, simple precautions minimise these effects, and they are not a serious obstacle to the introduction of an operational dosimeter. The most important remaining problem is that of the acceptability of the poor angular response of a single planar detector, and the possible need for an operational dosimeter to use multiple detectors with different orientations. (author)