Aquatic hyphomycetes have been reported from terrestrial root surfaces (Parkinson and Thomas, 1969; Taylor and Parkinson, 1965; Waid, 1954; Watanabe, 1975), bark (Fisher and Petrini, 1989, 1990; Fisher et al., 1991) and xylem (Fisher et al., 1991). Recent studies on aquatic root bark and xylem of Alnus glutinosa (L.) Gaertner (Fisher et al., 1991; Marvanovf and Fisher, 1991), Acer spicatum Lam., Betula papyrifera Marsh. and Picea glauca (Moench) Voss (Sridhar and Biirlocher, 1992) revealed about 20 species of endophytic aquatic hyphomycetes. Somewhat surprisingly in view of the scarcity of aquatic hyphomycetes on conifer needles, roots of white spruce yielded more species than maple or birch (Sridhar and Barlocher, 1992). Fungi were recovered both by plating and by aeration of surface sterilized bark and xylem segments. The present study had three objectives: 1) to study the effect of root age on the diversity of endophytic aquatic hyphomycetes in P. glauca; 2) to compare recovery of fungal species by aeration and plating techniques; and, 3) to estimate total fungal biomass of aquatic roots by determining their ergosterol content. All roots were collected from white spruce (Picea glauca (Moench) Voss) lining Boss Brook, a softwater stream in Fenwick, Nova Scotia, Canada (Barlocher, 1987). Root material submerged in flowing water was procured from five trees during June and July 1991. It was transported to the laboratory in polyethylene bags and processed within 4 h of recovery. Water temperature during the sampling period ranged between 11-13.5 C. The age of the root segments was estimated by counting annual rings of transverse sections under a low power microscope. Four age groups, viz. 2, 4-5, 9-10 and 14-15 yr, were selected for the study. Root diameters were