Effects of water and heat stress treatments on sugar contents of Chinese fir,Masson pine,Douglas fir and Western redcedar seedlings were measured during a three cycle stress period in spring 2001 at The University of British Columbia. The results were shown as follows:(1)There is no significant difference of fructose in Chinese fir needles under water and heat stress.But it was observed that there are significant differences of sucrose and glucose in Chinese fir needles under water and heat stress.The value of sucrose and glucose increase by 11.80% and 318.86% respectively under the bitter water stress and the value of sucrose and glucose increased by 16.54% and 169.83% respectively with the bitter heat stress.((2)Water) stress had significant effects on sucrose and glucose contents in Masson pine needles while heat stress had significant effects on fructose and glucose contents in Masson pine needles.And it was shown that all three sugars increase under bitter water and heat stress in Masson pine needles.The contents of glucose,fructose and sucrose were increased by (45.92%),(34.01%) and 138.32% respectively under water stress and by 36.07%,28.01% and 22.82% respectively under heat stress.(3)Although water and heat stress had significant effects on contents of all three sugars in Douglas fir,it was observed that contents of the three sugars had no apparent increase under the bitter water stress.And the apparent increase could be monitored under the bitter heat stress.(4)Water and heat stress treatments had significant effects on contents of all three sugars in Western redcedar.And the contents of glucose,fructose and sucrose were increased by 89.46%,(90.32%) and 71.68% respectively under the bitter water stress and by 21.18%,45.97% and 107.67% respectively under the bitter heat stress.The interaction of water and heat stress had only significant effects on sucrose content in Western redcedar needles.