Progress in mine lighting has been slow in most countries, particularly when compared to other lighting situations, yet sight is our most important sense. Good lighting systems, namely, those that provide sufficient illuminance for the task to be performed (see Table 2), are usually expensive, and it is often difficult to justify the expense to mine managers. With working places often spread out both laterally and vertically and with continual blasting in these areas, permanent installations are generally deemed impractical because of the costs of installation and upkeep. Consequently, the battery-operated cap lamp is usually the most important single source of light in an underground mine. According to a recently enacted mining law in Canada, “All cap lamps shall be capable of providing a peak illuminance of at least 1500 lux at 1.2 m from the light source throughout a working shift.” Similar regulations relating to cap lamp lighting underground have recently become law. These regulations were all enacted as a result of an extensive commission of inquiry into mine safety triggered by a multiple mine fatality. As a result of the inquiry, lighting research studies were conducted in several mines to establish optimum lighting conditions provided solely by the miner's cap lamp. The major findings of these studies were used to establish the present regulations. Initially, most cap lamp manufacturers could not meet the new standards with off-the-shelf cap lamp hardware. They responded to the new legislation by redesigning the cap lamp in spite of the practical problems. Improvements in battery technology, reflector material and configuration, and cap lamp bulb configuration have all resulted in a constant high light output and better light control for shifts lasting up to 10 hours. This article discusses the reasons for the initial inquiry, the results of the inquiry as they relate to portable underground lighting, the method of conducting studies to determine optimum light parameters to address the findings of the inquiry, the resulting legislation enacted in various provincial jurisdictions, the methods of measuring for compliance, the cap lamp manufacturers' improvements, and the system incorporated into law in Canada to ensure quality control.