The first atmospheric observations and trends are presented for the high molecular weight perfluorocarbons (PFCs): decafluorobutane (C₄F₁₀), dodecafluoropentane (C₅F₁₂), tetradecafluorohexane (C₆F₁₄), hexadecafluoroheptane (C₇F₁₆) and octadecafluorooctane (C₈F₁₈). Their atmospheric histories are based on measurements of 38 Northern Hemisphere and 46 Southern Hemisphere archived air samples collected between 1973 to 2011 using the Advanced Global Atmospheric Gases Experiment (AGAGE) "Medusa" preconcentration gas chromatography-mass spectrometry systems. A new calibration scale was prepared for each PFC, with estimated accuracies of 6.8% for C₄F₁₀, 7.8% for C₅F₁₂, 4.0% for C₆F₁₄, 6.6% for C₇F₁₆ and 7.9% for C₈F₁₈. Based on our observations the 2011 globally averaged dry air mole fractions of these heavy PFCs are: 0.18 parts-per-trillion (ppt, i.e., parts per 10¹²) for C₄F₁₀, 0.12 ppt for C₅F₁₂, 0.28 ppt for C₆F₁₄, 0.12 ppt for C₇F₁₆ and 0.09 ppt for C₈F₁₈. These atmospheric mole fractions combine to contribute to a global average radiative forcing of 0.35 mW m⁻², which is 3.6% of the total PFC radiative forcing. The globally averaged mean atmospheric growth rates of these PFCs during 1973–2011 are 4.58 parts per quadrillion (ppq, i.e., parts per 10¹⁵) per year (yr) for C₄F₁₀, 3.29 ppq yr⁻¹ for C₅F₁₂, 7.50 ppq yr⁻¹ for C₆F₁₄, 3.19 ppq yr⁻¹ for C₇F₁₆ and 2.51 ppq yr⁻¹ for C₈F₁₈. The growth rates of the heavy perfluorocarbons were largest in the early 1990s for C₄F₁₀ and C₅F₁₂ and in the mid-to-late 1990s for C₆F₁₄, C₇F₁₆ and C₈F₁₈. The more recent slow down in the growth rates of the high molecular weight PFCs suggests that emissions are declining as compared to the 1980s and 1990s. Nevertheless continued monitoring of these potent, extremely long-lived greenhouse gases is necessary to verify that global PFC emissions continue to decline.