The double-mutant ΔchkA ΔchkB showed increased sensitivity to UV light. Viability of the wild-type, ΔchkA, ΔchkB (A), ΔchkA ΔchkB (B), ΔatmA ΔchkA (C), ΔatmA ΔchkB (D), ΔuvsB ΔchkA (E), and ΔuvsB ΔchkB (F) germlings was scored after exposure to UV light of quiescent and germinating conidiospores. Viability was determined as the percentage of colonies on treated plates compared to untreated controls. The results were expressed by the average of three independent experiments and means ± standard deviations are shown. The ΔchkA and ΔchkA ΔchkB strains were significantly different from the wild-type and ΔchkB strains in germinating conidiospores, P < 0.02.