A one-piece shell chair (10) includes an unitary integrally formed shell body (12) having a flexurally supported seat pan (14) and a flexurally supported backrest (16) defined in part by an H-shaped opening (20) in the shell body. The backrest (16) and the seat pan (14) resiliently flex as independent units in response to an occupant's body shape, size, posture and positioning. Integral, flexible straps join the backrest (16) to the seat pan (14) to permit resilient flexing of the backrest (16) with respect to the seat pan (14) about an axis through the occupant's hip joint to minimize shear between the backrest and the occupant's back during flexing movement of the backrest 16 with respect to the seat pan 14. The seat (12) is mounted to a tilt mechanism (28) which pivots the seat (12) about an axis forward and below the front edge (14a) of the seat pan (14) enabling the user's feet to remain stationary on the floor. Accordingly the seat (12) and tilt mechanism (28) provide a comfortable, convenient and accommodating chair (10).