Complex biological events occur during the developmental process of the mosquito Anopheles gambiae (Giles). Using cDNA expression microarrays, the expression patterns of 13,440 clones representing 8,664 unique transcripts were revealed from six different developmental stages: early larvae (late third instar/early fourth instar), late larvae (late fourth instar), early pupae (<30 min after pupation), late pupae (after tanning), and adult female and male mosquitoes (24 h postemergence). After microarray analysis, 560 unique transcripts were identified to show at least a fourfold up- or down-regulation in at least one developmental stage. Based on the expression patterns, these gene products were clustered into 13 groups. In total, eight genes were analyzed by quantitative real-time polymerase chain reaction to validate microarray results. Among 560 unique transcripts, 446 contigs were assigned to respective genes from the An. gambiae genome. The expression patterns and annotations of the genes in the 13 groups are discussed in the context of development including metabolism, transport, protein synthesis and degradation, cellular processes, cellular communication, intra- or extra-cellular architecture maintenance, response to stress or immune-related defense, and spermatogenesis.