Sunshine fraction, cloud amount, temperature, and global irradiation are the most commonly measured meteorological parameters. In this article five models based mainly on the above mentioned variables for the determination of the irradiation and illuminance components are presented. These models are divided into three categories. Category 1 includes three solar radiation models: (a) Meteorological Radiation Model (MRM), developed by present authors based on sunshine fraction and temperature data, (b) Cloud-Cover Radiation Model (CRM)-modification of an earlier model for the UK by the present authors based on cloud-cover in oktas, and (c) Page Radiation Model (PRM), developed by Page based on simultaneous sunshine and cloud data. Category 2 comprises of a new Diffuse Ratio Model (DRM), developed by authors, for estimating diffuse irradiation when global irradiation is provided as the input parameter. The third category includes luminous efficacy models that enable estimation of diffuse and global illuminance once the respective irradiation components have been obtained from Category 1 models. [S0199-6231(00)02003-7].