The response to glucose availability in Neurospora crassa was characterized by measuring transcript levels of 1335 genes represented on a cDNA microarray. We found that 19% of the 1335 genes were regulated at least twofold in response to glucose deprivation. Several sugar transporter homologs were found to be regulated by glucose. Functional analysis of one of these, hgt-1, indicates that it encodes a high-affinity glucose transporter. Comparing N. crassa profiling data with the published diauxic shift data from Saccharomyces cerevisiae revealed that the two fungi share similar, but not identical, transcriptional response patterns. Regulation of transcript levels measured by microarray analysis is consistent with previous measurements of central metabolism enzyme activities for N. crassa. Transcripts of genes for ethanol fermentation and the tricarboxylic acid cycle are abundant in glucose-rich medium, consistent with N. crassa carrying out a high rate of both fermentation and respiration simultaneously.