Changes in the chemical shifts for butyl (BAP), hexyl (HAP), octyl (OAP), decyl (DeAP), and dodecyl (DAP) ammonium propionates in benzene and in carbon tetrachloride as functions of their concentrations have established the formation of micelles. Treatment of the 1H n.m.r. data afforded values for the critical micelle concentration, the aggregation number and the equilibrium constant for the formation of micelles in benzene listed in sequence as follows: BAP, (4.5–5.5)× 10–2 M, 4, 1 × 104 M1–n; HAP, (2.2–3.2)× 10–2 M, 7, 5 × 102 M1–n; OAP, (1.5–1.7)× 10–2 M, 5, 1 × 108 M1–n;; DeAP, (8–10)× 10–3 M; DAP, (3–7)× 10–3 M, and those in carbon tetrachloride: BAP, (2.3–2.6)× 10–2 M, 3, 9 × 102 M1–n; HAP, (2.1–2.4)× 10–2 M, 7, 7 × 1011 M1–n; OAP, (2.6–3.1)× 10–2 M, 5, 5 × 107 M1–n; DeAP, (2.2–2.7)× 10–2 M, 5, 1 × 107 M1–n; DAP, (2.1–2.5)× 10–2 M, 4, 5 × 104 M1–n. These micelles have their polar head groups in the interior of the aggregate while the hydrophobic carbon chain is in contact with the non-polar solvent.