Adjunctive intraoperative photodynamic therapy (AIOPDT) is a technique in which a large surface area of tumour bed receives photodynamic therapy (PDT) immediately after surgical resection. This has been practised clinically and has been shown experimentally to decrease subsequent local recurrence. Existing light delivery systems (LDSs) for this particular application of PDT are inadequate and without accurate and uniform light dosimetry, the therapy cannot be expected to work. We have defined essential criteria that efficient and effective LDSs should meet for AIOPDT, and have designed, constructed, tested and used in patients three LDSs meeting these criteria in order to irradiate different geometries. The term ‘uniformity ratio’ (UR) has been introduced and defined as the maximum to minimum energy density over a target. These LDSs provide a UR of less than 1.6 and thus a well-controlled, uniform light dose can be applied over a large surface area. A total of 30 patients have been treated with no complications attributable to AIOPDT. Accurate light dosimetry is essential if AIOPDT is to progress and these LDSs are a significant improvement over existing systems.