A computer programme for the static worst-case design of a diode-transistor logic element is described. The approach adopted permits the designer to take into account the possible existence of voltage and current-operated loads other than identical logic elements which the element may be called upon to drive. The computer results comprise a complete listing of all sets of standard resistor values capable of providing a specified fan-out factor for given supply line and resistor tolerances and given diode and transistor parameters. By eliminating much tedious calculation and narrowing the field these solutions form useful starting points from which the engineer may proceed to a final design satisfying all the imposed conditions.