Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi-221 005 Manuscript received 6 September 1977, revised 19 September 1978, accepted 21 December 1978 N-Ƥ-Tolyl (or phenyl)-N'-(substituted) benzothiazol-2-yl thiocarbamides were reacted with primary alkylamines in presence of yellow lead oxide to afford N-Ƥ-tolyl (or phenyl)­N'-(substituted) benzothiazol-2yl-N"-alkylguanidines. The structures of these guanidines have been stabilished on the basis of the elemental analysis and spectral data. Among the two series of the synthesised compounds the Ƥ-tolyl analogues (Ia-If) have been screened for antibacterial and fungicidal activities and phenyl analogues (II3_d, lIla-c and IVa-d) for their CNS activity. It has been observed that the halogen substituent in the heterocyclic benzothiazole ring enhanced the activity of the compound.