This randomized, six-treatment, six-period, six sequence, single dose, crossover pharmacokinetic study assessed the effect of different types of food on the bioavailability of 500-mg cefaclor extended release tablet in 23 healthy male volunteers. A single dose of cefaclor extended release 500-mg tablet was administered at six occasions: after overnight fasting, after two vegetarian (high-fat and low-fat), two non-vegetarian (high-fat and low-fat) and rice diets. Serial blood samples were collected up to 12 h after dose. Serum cefaclor concentrations were determined by a validated HPLC method. An almost equivalent increase in both Cmax and AUC was observed with both high-fat non-vegetarian and low-fat vegetarian breakfasts. However, when MIC90 values, a pharmacodynamic end-point were compared, the low-fat vegetarian diet fared better than the high-fat non-vegetarian diet. The results obtained favor low-fat vegetarian diet (breakfast) to be taken with cefaclor extended release tablet to achieve maximum benefit in terms of clinical efficacy.