Abstract 1. objective: the objective of the present study was to formulate a novel topical spray formulation comprising aceclofenac and other non-toxic excipients using (mixture of propane and butane) lpg as propellant. study was designed to characterize and evaluate different formulation. an optimum formulation was to be investigated for skin irritation study, in-vivo anti inflammatory study and finally stability study. marketed product would be compared with an optimum formulation to check the feasibility of new formulation. 2. experimental work: the preformulation studies for drug aceclofenac was carried out and compatibility of drug in formulation with different excipients was checked. primary screening of variables like penetration enhancers and solvents were done by preparing trial batches. final batches were prepared comprising of penetration enhancers such as tulsi oil and octyl salicylate, solvent and co-solvent such as iso propyl alcohol and ethanol respectively, and other excipients like counter irritant, cooling agent and humectants using 22 full factorial design. prepared aceclofenac topical spray formulations were evaluated for different parameters. in-vivo skin irritation study and anti inflammatory study in carrageenan induced hind paw edema model were carried using albino rats for optimised formula tb4 and results were compared with marketed gel formulation. finally, optimised formula tb4 was kept for stability study as per ich guidelines. 3. results and discussion: absence of physical and chemical incompatibility during compatibility study revealed that aceclofenac is compatible with container closure and excipients. aceclofenac topical spray formulation tb4 was found to be the best formulation evaluation data of different formulation for physico-chemical test, performance test and ex-vivo diffusion studies indicated the effectiveness of tulsi oil as penetration enhancer. tb4 was further proved non irritant and therapeutically more effective than marketed gel formulation. the stability study in accordance with ich guidelines indicated that the optimised formulation was stable. 4. conclusions: a novel type of formulation comprised of aceclofenac, tulsi oil and organic volatile and non volatile solvents, was used to develop a new topical spray formulation. this novel topical spray formulation was transparent solution with good, early evaporation and ease of application. in addition the research results showed the resultant invisible thin film with excellent carrier properties and crystallization inhibition function of linseed oil and enhanced effect of tulsi oil on drug permeation. finally, skin irritation test and in-vivo anti inflammatory test proved that the spray formulation was safe to be used for topical delivery. in summary, the novel formulation of aceclofenac, tulsi oil, linseed oil and other excipients may provide alternate dosage form to aceclofenac gel formulation.