The relationship between (Q) total solar radiation, as measured by a solarimeter, and hours of bright sunshine (n), as measured by a Campbell-Stokes recorder, has been examined on a monthly basis for three tropical stations Madras, Waltair and Nagpur. The regression equations relating the data are calculated in the non-dimentional form of Angstrom type $$Q = Q_A \left( {a + b\frac{n}{N}} \right)$$ whereQA is the maximum possible radiation andN in the maximum possible duration of bright sunshine. The individual regression relationships for the three stations are also verified; the agreement between the computed values and observed solar radiation is good. It has been shown that the slope of the relationshipb is approximately constant, while the value ofa is a function of latitude. An empirical relationship leading to the Angstrom equation at latitude θ over the range 0°–60° as derived byGlover andMcCulloch [13]2) gives values in reasonable accord. A combined equation for the three stations of the form $$Q/Q_A = 0.29 \cos \phi + 0.51\frac{n}{N}$$ has been presented. The sum ofa andb has been shown to lie around a mean of 0.77, in good agreement with the other workers.