Gullies proliferate the landscape of the Ajalli Sandstones (AS) geological formation in the North Central Nigeria. This study was carried out to assess the vulnerability to gully erosion of the Ajalli Sandstones geological sediments, and to examine the relationship between gully length and average gully sediment volume on this formation. Soil samples, collected from each sidewall of 15 gully erosion sites at two depth ranges, the rilling depth, d1 (0 – 60 cm) and the gullying depth, d2 (60 – 120 cm), were tested to determine their particle size distribution using the hydrometer method as well as compute their erodibility indices (K). Further, samples were collected using sampling tubes to determine the soils’ dry bulk density (DBD). Additionally, 37 gullies developed on the AS formation were measured to determine their lengths (L), average widths (W), and average depths (D). From each gully, three additional variables of average gully sediment volume (V), average cross sectional area (A), and average form factor (W/D) were computed. For the two respective depth ranges, the particle size distributions, the K values, and the DBD as well as the sets of six variables of L, W, D, C, A, and W/D from each gully were analysed using descriptive statistics. And the pairs of L and V for each gully were further analysed using inferential statistics to examine their relationship. Results show that the rilling depth (d1) and the gullying depth (d2) are both highly erodible with the mean %sand d1 + %siltd1 = 95%, %clayd1 = 5%, Kd1 = 24.40, and DBDd1 = 1.31 g/cm3; and the mean %sandd2 + %siltd2 = 82%, %clayd2 = 18%, Kd2 = 8.40, and DBDd2 = 1.34 g/cm3. The cross sectional shape of the gullies formed on the AS is trapezoidal. The mean W/D ratio on this formation is 1.46. This shows that the surface soil is eroding faster than the subsurface soil. The length is significantly, positively, but moderately correlated with the average sediment volume. And a simple bivariate regression shows that the relationship between gully length and the average gully sediment volume is of the form: V = 27,066.643 + 147.213L (R = 0.503, R2 x 100 = 25.30%). The study also shows that gully length is a moderate predictor of average sediment volume on homogeneous, erodible formations.