By going to the patient to dispense drugs and provide a therapeutic monitoring, the home care service clinical pharmacist must be able to certify that medications do not undergo degradation by heat, humidity, gas or light. ln this study, three simple evaluation methods for the light permeability of plastic bags have been investigated. The first method is based on the photography principle. It enables a qualitative comparison of the protection provided by different plastic materials. The second method consists of studying the permeability of plastic bags directly in a spectrophotometer. Finally, the degradation of photosensitive substances introduced into the plastic bags can also be monitored by spectroscopic measurements. ln this case, the substances used were vitamin K1, chlorpromazine hydrochloride and nifedipin. These three methods are complementary and require a simple set-up. They enable a quick analysis of plastic bags permeability to light, which is very useful for a home care service clinical pharmacist.