3,4-Dihydro-2H-1,3-benzoxazines derivatives are a significant class of heterocycles with particular awareness due to their remarkable biological activities in humans, plants and animals, and also their natural occurrence. Alteration in the benzoxazine skeleton and their comparative chemical simplicity and accessibility, make these compounds suitable sources of other bioactive compounds, resulting in the discovery of a wide set of these compounds that have broad biological activity, such as antifungal, antibacterial, anti-HIV, anticancer, anticonvulsant, anti-inflammatory, etc. Subsequently, this review gives herein a brief overview of the chemistry and bioactivities of derivatives of 3,4monomers and their oxo-derivatives. (Received 30 May, revised 3 December 2018, accepted 11 January 2019) Abstract: 3,4-Dihydro-2H-1,3-benzoxazines derivatives are a significant class of heterocycles with particular awareness due to their remarkable biological activities in humans, plants and animals, and also their natural occurrence. Alteration in the benzoxazine skeleton and their comparative chemical simplicity and accessibility, make these compounds suitable sources of other bioactive compounds, resulting in the discovery of a wide set of these compounds that have broad biological activity, such as antifungal, antibacterial, anti-HIV, anticancer, anticonvulsant, anti-inflammatory, etc. Subsequently, this review gives herein a brief overview of the chemistry and bioactivities of derivatives of 3,4-dihydro-2H-1,3-benzoxazine monomers and their oxo-derivatives. Keywords: 1,3-benzoxazines; synthesis; reactions; biological activities.