Abstract: It is proved that there exist two positive numbers λ ^*,λ_*, with 0<λ^*<λ_*<+∞, such that the singular nonlinear fourth order boundary value problems y⁽⁴⁾(x)=λh(x)f(y(x)),0*) and have a positive soluti on for λ∈(λ^*,+∞) and for λ∈(λ_*,+∞), there are three sol utions, two of which are positive solutions, provided that f(y) is superlinear at y=0 and sublinear at y=+∞.

Key words: singularity, positive solution, cone, fixed point