This paper proposes scintillation cameras which can handle input pulse rates beyond 1 Mcps with negligible as spatial resolution and energy resolution at low pulse rates. The cameras are based on the "variable sampling-time technique", in which phototube current pulses are first shortened in width and then selectively integrated by gated integrators followed by sample-and-hold circuits. The period of integration before sampling is not fixed but shortened by the arrival of the following pulse to keep a high pulse-pair time resolution. An approximate expression for the count rate characteristics has been derived, and its validity was confirmed by Monte Carlo simulation. The results indicates that the maximum observed count rate will reach 420-520 kcps with an energy window fraction of 0.5 for typical design parameters.