The paper presents the INTCAL98 calibration curve for radiocarbon ages ranging from 24,000 to 0 cal BP, based on dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediments. The authors discuss offsets in measured 14C ages, regional 14C age differences, tree-coral 14C age comparisons, and the time dependence of marine reservoir ages. They evaluate decadal vs. single-year 14C results and changes in oceanic deepwater circulation, particularly for the 16,000–11,000 cal BP interval. The INTCAL98 calibration curve is constructed using a combination of decadal and single-year 14C data, with a focus on improving the accuracy and precision of age estimates. The paper also addresses hemispheric and regional offsets, tree-ring and coral 14C age differences, and marine reservoir age considerations. The marine calibration curve reflects global open ocean conditions, with regional departures expressed as ΔR parameters. The Δ14C profile for 15,500–0 cal BP and 40,000–0 cal BP is discussed, highlighting long-term trends and century-scale variations. The authors recommend specific guidelines for regional offsets and provide recommendations for age calibration using computer programs that incorporate the INTCAL98 database.The paper presents the INTCAL98 calibration curve for radiocarbon ages ranging from 24,000 to 0 cal BP, based on dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediments. The authors discuss offsets in measured 14C ages, regional 14C age differences, tree-coral 14C age comparisons, and the time dependence of marine reservoir ages. They evaluate decadal vs. single-year 14C results and changes in oceanic deepwater circulation, particularly for the 16,000–11,000 cal BP interval. The INTCAL98 calibration curve is constructed using a combination of decadal and single-year 14C data, with a focus on improving the accuracy and precision of age estimates. The paper also addresses hemispheric and regional offsets, tree-ring and coral 14C age differences, and marine reservoir age considerations. The marine calibration curve reflects global open ocean conditions, with regional departures expressed as ΔR parameters. The Δ14C profile for 15,500–0 cal BP and 40,000–0 cal BP is discussed, highlighting long-term trends and century-scale variations. The authors recommend specific guidelines for regional offsets and provide recommendations for age calibration using computer programs that incorporate the INTCAL98 database.