Dried seeds of maize inbred lines were carried by recoverable satellite to space conditions at an altitude of 175-253 km from sea level for 15 d. The effects of space flight on ultrastructure and photosynthetic pigment contents of maize leaves were studied. Various changes in structure were observed. Chloroplast envelope membrane notch, swelling of thylakoids, less granum stacks and stroma thylakoid membranes, and changes of chloroplast contour were often seen. The contents of chlorophyll a, chlorophyll b, and chlorophyll a+b and carotenoids tended to be lower, but Ca/Cb ratio tended to be higher in the leaves from space flight maize in comparison with ground control.