Roughly described, method and apparatus for laying out an integrated circuit, in which a subject interconnect has predetermined values for a plurality of variables affecting propagation delay of the subject interconnect. The value of an adjustment one of the variables is adjusted to minimize exposure of the propagation delay of the interconnect to process variations causing variations in the value of a subject fabrication variable, and a revised layout is developed in dependence upon the adjusted value for the adjustment variable. In an embodiment, the adjustment is made in dependence upon a pre-calculated “interconnect optimization database” indicating combinations of values for the plurality of variables which have been pre-determined to minimize exposure of interconnect propagation delay to process variations affecting the subject variable. Different databases, or different entries in the same database, can be provided for minimizing exposure of interconnect propagation delay to process variations affecting each subject variable of interest.