Hello, I have installed nVidia CUDA 4.2 on my Macbook 5,1 (Aluminum, late 2008). Installation went fine, following the instructions from this guide. Examples were compiled successfully and some of them were run as well. I have compiled a .cu file using the below code: Code: $ nvcc -c -o cuda.o program.cu Then compiled using g++ and got the following message: Code: $ g++ -o b cuda.o ld: warning: ignoring file cuda.o, file was built for i386 which is not the architecture being linked (x86_64): cuda.o Undefined symbols for architecture x86_64: "_main", referenced from: start in crt1.10.6.o ld: symbol(s) not found for architecture x86_64 collect2: ld returned 1 exit status I am suspecting that CUDA is not using the 64-bit libraries, since I had a similar experience with Ubuntu a few days ago. Does anyone know how this can be fixed?