We have combined photochemistry and photolithography with solid-phase DNA synthesis chemistry to form a new technology that makes high density oligonucleotide probe array synthesis possible. Hybridization to these two-dimensional arrays containing hundreds or thousands of oligonucleotide probes provides a powerful DNA sequence analysis tool. Two types of light-generated DNA probe arrays have been used to test for a variety of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. One array, made up of 428 probes, was designed to scan through the length of CFTR exon 11 and identify differences from the wild type reference sequence. The second type of array contained 1480 probes chosen to detect known deletions, insertions, or base substitution mutations. The validity of the probe arrays was established by hybridizing them with fluorescently labeled control oligonucleotide targets. Characterized mutant CFTR genomic DNA samples were then used to further test probe array hybridization specificity. Finally, ten unknown patient samples were genotyped using the CFTR probe array assay. The genotype assignments were identical to those obtained by PCR product restriction fragment analysis. Our results show that light-generated DNA probe arrays are highly effective in analyzing complex mutation and polymorphism patterns in a relatively large gene such as CFTR.