Crude olive pomace oil (COPO) and crude soybean oil (CSO), two low-cost carbon sources, were examined as cosubstrates of glucose for carotenoid production by Blakeslea trispora. Results were compared to those obtained in glucose as a sole carbon source (medium 1) and glucose plus the respective end-line refined oil counterparts. Microbial growth in the presence of oils resulted in an increase in total carotenoid production. The performance of crude oils was better than that of the respective refined forms. Carotenoid production depended on both type and added oil amount. An increase in added oil amount did not necessarily favor carotenoid accumulation. The addition of 10 g oil/L of substrate stimulated carotenoid synthesis, mainly that of beta-carotene, more than 14 (COPO) and 40 times (CSO) in comparison to that observed in medium 1. The maximum total carotenoid content (as mg beta-carotene per g of biomass dry weight) was 75 (COPO) and 235 mg (CSO), respectively. Growth, substrate assimilation, and lipid accumulation-degradation also depended on the presence of oil in the substrate.