The Solomon R. Guggenheim Museum in New York City, designed by Frank Lloyd Wright, is one of the most unusual concrete buildings ever built. Its construction was described in the March 1958 issue of CONCRETE CONSTRUCTION, page 10. But it is one thing to design and build the unusual and quite another to predict its performance over the long run. How is it doing now? There have been no cracks affecting the building structure. This is not to say the building is crack-fee but that problems with cracks have been minor. Inside the building, for example, some cracks have developed in the plaster finish over the curtain walls were inclined metal from skylights on top, connecting to the floor above, transmit differential movements. A simple expansion bead in the right place might have eliminated the problem. The high priority given to maintenance is a big factor in explaining why no major problems have developed. A regular 4 to 5 year program of waterproofing and painting the outside surfaces is followed. Several maintenance problems arose with the waterproofing in the first few years- probably from using waterproofing materials not entirely compatible with this type of building. Exterior surfaces had originally been sprayed with a vinyl-impermeable membrane. This blockage of moisture asked vapor migrating through the concrete from inside the building to accumulate from behind the vinyl coating and erupt as blisters on the surface. Blistering has never been excessive serious at any one time so it is dealt with on a spot treatment basis. The building superintendent emphasizes that all the problems he has experienced- surface cracking, leakage, blistering, and condensation behind finished walls- are minor and that structural maintenance is probably the least expensive item in his budget.