Losses of delayed-neutron precursors are estimated for liquid-metal-fueled reactor models in which the coolant is in direct contact with the flowing fuel. It is shown that as much as 90% of the precursors may be extracted by the coolant before decaying to supply neutrons. As a result, the excess reactivity corresponding to prompt critical can decrease by a factor of 10, leading to a considerable shortening of the reactor period corresponding to a given Δk. These conditions will, in actual operation at power, be alleviated by the contribution of the blanket's delayed neutrons and by the large negative temperature coefficient characteristic of liquid systems. The effects of mixing and reduced flow on delayed-neutron economy and resulting reactor period are evaluated. The benefits of reducing the flow are shown to be by far the greater, and a slower flow is recommended if enhanced control through delayed neutrons is needed at start-up.