Photodynamic therapy (PDT) involves the use of a photosensitizer, which, when activated by light becomes toxic to the cancer cells. Lasers provide light at a specific wavelength required to activate the photosensitizer while the monochromaticity of the lasers at specific wavelengths results in maximum effectiveness of the photosensitizer during treatment. An important property of photosensitizers is that they should absorb light at a long wavelength as the light has to be able to penetrate tissue, and low energy light is able to travel further through tissue than light which absorbs at a shorter wavelength. This study aimed at evaluating the effects of 2 different photosensitizers, Al (AlPcSmix), commercially known as Photosens(R) and Ge (GePcSmix), both from the Phthalocyanine family of sensitizers, on oesophageal (SNO) and breast cancer (MCF-7) cells. Cells were irradiated at 660nm with a power output of 100 mW and a fluence of 10 J/cm2. Cell viability and proliferation were assessed using adenosine triphosphate (ATP) luminescence and alamarBlueTM staining. Lactate dehydrogenase (LDH) activity was used as a measure of cytotoxicity while the Comet assay was used to evaluate DNA damage. Heat shock protein 70 (Hsp70) induction acted as a measure of cellular stress. Both photosensitizers used during the course of this study are effective in targeting malignant cells, and have a cytotoxic effect on these cells when activated using laser irradiation. However, cytotoxic effects were also measured in the absence of laser irradiation, indicating the importance of photosensitizer concentration. Lower concentrations of photosensitizer in the presence of laser irradiation showed greater apoptotic inducing ability than with high concentrations. Morphologically, cells were affected to the detriment despite viability tests indicating the contrary.