Conditions for a natural fermentation during ensilage of sardines or their waste in sugarcane molasses (60:40 w/w) were evaluated regarding the effect of temperature (15, 25 and 35 degreesC), anaerobiosis (closed vs. open jars), daily stirring of the Mixture, and salt addition to the initial mix at 5% (w/w) level. Successful natural fermentation took place in sardine silages incubated at 25 or 35 degreesC in open jars to reach a pH of 4.4 in about 2 and 1 weeks, respectively. For samples kept at 15 degreesC, the pH decline was very slow and pH did not decrease below 5.5 after one month of incubation. At 25 degreesC, the most favorable conditions for silage of sardine waste in cane molasses, as evidenced by the fastest decline in pH to a stable value of about 4.4, were achieved in closed jars and with daily stirring of the mix. The pH 4.4 was reached in one week with an advance of at least 3 days compared to the other conditions (open jars and closed jars without daily stirring). Addition of salt at 5% (w/w) in the mix before incubation inhibited the fermentation process.