Flow cytometry-based immunophenotyping assays have become increasingly multiparametric, concomitantly analyzing multiple cellular parameters. To maximize the quality of the information obtained, antibody conjugate panels need to be developed with care, including requisite controls at every step. Such an optimization procedure for multicolor immunophenotyping assays is time consuming, but the value of having a reliable antibody conjugate panel that provides for sensitive detection of all molecules of interest justifies this time investment. This article outlines important considerations and procedures to undertake for the successful design and development of multicolor flow cytometry panels.