Research on fog climatology and cloud water interception (CWI) in the montane cloud forests of Hawai'i spans nearly 50 years, from the pioneering work of Wendell Mordy and Paul Ekern on Lâna'i in the 1950s, through the continuing efforts of James Juvik since 1972. This work has helped to improve understanding of the spatial patterns of fog occurrence and to quantify CWI in forests and other vegetation. Reported CWI or fog incidence estimates are as high as 4982 mm year−1 at particularly exposed locations, although most windward sites within the cloud zone are in the range between 280 and 1130 mm year−1, with leeward sites receiving between 100 and 500 mm year−1, and less than 250 mm year−1 in high-elevation areas above the trade-wind inversion. Most of the early work was based on mechanical fog gage measurements whose well-known limitations make accurate estimation of actual CWI by a forest canopy difficult. Advancing the current level of understanding will have to come from studies incorporating other methods, such as the wet-canopy water budget and stable isotope mass balance approaches, in addition to the continued use of recording fog and throughfall gages.