Novel series of 2-substitutedamino-4-(1-substitutedthiocarbamido-3-yl)-6-substitutedimino-1,3,5-thiadiazines[2a(i) to 2f(iii)] have been obtained by basification of their hydrochloride [1a(1) to 1f(iii)],which are prepared by the interaction of 1,3-Bis-(n- substitutedthioamido) guanidine and substitutedisocyanodichloride. The latter were prepared initially by the condensation of aryl/alkylisothiocyanate and guanidine carbonate in 1:2 molar ratios. The structure of all these compounds were established on the basis of elemental analysis, IR and PMR spectral data. All the synthesized compounds have been assayed for their antibiological activity against both gram-positive and gram-negative human pathogens and found that they possess insecticidal, and bacteriocidal.  Some 1,3,5-thiadiazine compounds show remarkable biological activity.