Structures for 3D sense amplifiers for 3D memories are disclosed. A first embodiment uses one type of vertical transistors in constructing 3D sense amplifiers. A second embodiment uses both n- and p-type transistors for 3D sense amplifiers. Either or both of n- and p-type transistors are vertical transistors. The n- and p-type transistors may reside on different levels, or on the same level above a substrate if both are vertical transistors. In any embodiment, different options are available for gate contact formation. In any embodiments and options or alternatives thereof, one or more sense-enable circuits may be used. Sense amplifiers for several bit lines may be staggered on one or both sides of a memory array. Column multiplexers may be used to couple particular bit lines to data outputs. Bit-line multiplexers may be used to couple certain bit lines to shared 3D sense amplifiers.