An ultrasonic instrument comprising: (a) an ultrasonic transducer (26, 126), wherein the ultrasonic transducer is operable to convert electrical power into ultrasonic vibrations; (b) an acoustic waveguide (28, 128) in acoustic communication with the ultrasonic transducer, wherein the acoustic waveguide defines a longitudinal axis; and (c) an ultrasonic blade (24, 130) in acoustic communication with the acoustic waveguide such that the ultrasonic transducer is operable to drive the ultrasonic blade to vibrate ultrasonically via the acoustic waveguide; wherein the ultrasonic blade includes a pair of obliquely extending edges (222, 232, 320, 322, 330, 332, 420, 422, 430, 432, 520, 522, 530, 532, 620, 622, 630, 632), wherein the obliquely extending edges diverge away from the longitudinal axis and away from each other along respective paths extending distally in relation to the acoustic waveguide; wherein the ultrasonic blade further comprises a laterally presented concave surface (216, 316, 416, 516, 616) located between the obliquely extending edges, wherein the ultrasonic blade further comprises a laterally presented convex surface (218, 318, 418, 518, 618) on the opposite side of the blade to the concave surface, wherein the ultrasonic blade further includes a convexly curved distal edge (210, 310, 410, 510, 610) extending between the obliquely extending edges, wherein the ultrasonic blade further includes a first laterally presented surface (212, 312, 412, 512, 612) extending proximally from the distal edge, wherein the first laterally presented surface is partially bound by a curved proximal edge (214, 314, 414, 614), and wherein the concave surface (216, 316, 416, 516, 616) is proximal to the first laterally presented surface (212, 312, 412, 512, 612); characterized in that either: the first laterally presented surface (212, 312, 412, 512, 612) is flat; or the first laterally presented surface (212, 312, 412, 512, 612) is convex and has a curvature along a first plane defined by a first radius, wherein the concave surface (216, 316, 416, 516, 616) has a curvature along a second plane defined by a second radius, wherein the first plane and the second plane are parallel, wherein the first and second plane are perpendicular to the longitudinal axis, wherein the first radius is greater than the second radius, wherein the first and second radii extend away from their respective surfaces in opposite directions. (a) an ultrasonic transducer (26, 126), wherein the ultrasonic transducer is operable to convert electrical power into ultrasonic vibrations; (b) an acoustic waveguide (28, 128) in acoustic communication with the ultrasonic transducer, wherein the acoustic waveguide defines a longitudinal axis; and (c) an ultrasonic blade (24, 130) in acoustic communication with the acoustic waveguide such that the ultrasonic transducer is operable to drive the ultrasonic blade to vibrate ultrasonically via the acoustic waveguide; the first laterally presented surface (212, 312, 412, 512, 612) is flat; or the first laterally presented surface (212, 312, 412, 512, 612) is convex and has a curvature along a first plane defined by a first radius, wherein the concave surface (216, 316, 416, 516, 616) has a curvature along a second plane defined by a second radius, wherein the first plane and the second plane are parallel, wherein the first and second plane are perpendicular to the longitudinal axis, wherein the first radius is greater than the second radius, wherein the first and second radii extend away from their respective surfaces in opposite directions.