The synthesis, properties, and application in electronic devices of ladder and step-ladder phenylene-based oligomers and polymers are reviewed with an emphasis on control of properties by synthetic design. Bridged polyphenylenes can be prepared with a range of different amounts and types of bridges. Fully bridged polymers suffer the problem of incomplete formation of bridges during polymer analogous reactions. This problem is surmounted by the synthesis of regular stepladder polymers in which the monomers are well-characterized oligo(ladder-phenylene)s. By controlling the degree of bridging and thus the planarity of the polymer, its optical properties can be tuned. The optical and electronic properties can be further controlled by means of the type of bridges used.