The authors describe a sequential strategy for designing manufacturable integrated circuits using available CAD tools. Optimizing the performance of complex designs in the presence of unwanted parameter variations can take a prohibitively large number of computer runs. These methods overcome this complexity by combining sequential experimentation with modeling of the CAD simulator output as realizations of stochastic processes. These models give inexpensive approximations that enable location of subregions on which to continue the search for the optimal design. The multistage experimentation reduces the number of simulation runs required to obtain sufficiently accurate approximations. The strategy is able to treat circuits with many parameters, performances, and criteria. Included are two examples where improved designs have been found by these methods. The first is a zero-temperature-coefficient current reference IC. The second is a gallium arsenide voltage level shifter IC with multiple performances of interest.>