OBJECT: There is scant and conflicting information in the literature regarding the lateral lacunae, or lateral lakes of Trolard. As these venous structures can be encountered surgically, this study aimed at further elucidating their anatomy, identifying surgical landmarks, and associated quantitation. METHODS: Thirty-five adult cadavers were dissected of lateral lacunae. Following quantitation of the lacunae, these structures were measured, as were the distances from them to the coronal and sagittal sutures. RESULTS: A mean of 1.9 lacunae were identified on the right sides and 1.4 lacunae on the left sides. Although there tended to be slightly more lacunae on the right sides, this difference did not reach statistical significance (p > 0.05). The average lengths of the lacunae were 3.2 and 2.0 cm for the right and left sides, respectively. The mean widths of these venous lakes were 1.5 cm for the right sides and 0.8 cm for the left sides. Lacunae were variably positioned but tended to cluster near the vertex of the skull. None were identified posterior to the lambdoid sutures, and only 5 were found to lie anterior to the coronal suture, with 4 of these located on right sides (p < 0.05). When lacunae were identified anterior to the coronal suture, they were generally 5-6 cm from this structure. The majority of lacunae could be identified between the coronal and lambdoid sutures and within 3 cm of the midline. CONCLUSIONS: Although the situation varies, lateral lacunae are concentrated posterior to the coronal suture and anterior to the lambdoid sutures. They are most often found within 3 cm of the sagittal suture. These previously unreported data could be useful to the neurosurgeon in planning surgical procedures that traverse the calvaria.